Added usage instructions for NS Update Software Change and Remove VNF

Policy update changes are performed on running VNF instance unless `software-version` is changed in the new revision of VNFD.

TODO: write the alterable parameters

Policy update can be used to update all the parameters related to policies like scaling-aspect and healing.

```yaml

     +--rw vdu* [id]

     |  +--rw scaling-aspect* [id]

     |  |  +--rw id                               string

     |  |  +--rw name?                            string

     |  |  +--rw description?                     string

     |  |  +--rw max-scale-level?                 uint32

     |  |  +--rw aspect-delta-details

     |  |  |  +--rw deltas* [id]

     |  |  |  |  +--rw id                             string

     |  |  |  |  +--rw vdu-delta* [id]

     |  |  |  |  |  +--rw id                     -> ../../../../../../vdu/id

     |  |  |  |  |  +--rw number-of-instances?   uint32

     |  |  |  |  +--rw virtual-link-bit-rate-delta* [id]

     |  |  |  |  |  +--rw id                       string

     |  |  |  |  |  +--rw bit-rate-requirements

     |  |  |  |  |     +--rw root    uint32

     |  |  |  |  |     +--rw leaf?   uint32

     |  |  |  |  +--rw scaling:kdu-resource-delta* [id]

     |  |  |  |     +--rw scaling:id                     -> ../../../../../kdu-resource-profile/id

     |  |  |  |     +--rw scaling:number-of-instances?   uint32

     |  |  |  +--rw step-deltas?   -> ../deltas/id

     |  |  +--rw scaling:scaling-policy* [name]

     |  |  |  +--rw scaling:name                        string

     |  |  |  +--rw scaling:scaling-type?               common:scaling-policy-type

     |  |  |  +--rw scaling:enabled?                    boolean

     |  |  |  +--rw scaling:scale-in-operation-type?    common:scaling-criteria-operation

     |  |  |  +--rw scaling:scale-out-operation-type?   common:scaling-criteria-operation

     |  |  |  +--rw scaling:threshold-time              uint32

     |  |  |  +--rw scaling:cooldown-time               uint32

     |  |  |  +--rw scaling:scaling-criteria* [name]

     |  |  |     +--rw scaling:name                              string

     |  |  |     +--rw scaling:scale-in-threshold?               decimal64

     |  |  |     +--rw scaling:scale-in-relational-operation?    common:relational-operation-type

     |  |  |     +--rw scaling:scale-out-threshold?              decimal64

     |  |  |     +--rw scaling:scale-out-relational-operation?   common:relational-operation-type

     |  |  |     +--rw scaling:vnf-monitoring-param-ref?         string

     |  |  +--rw scaling:scaling-config-action* [trigger]

     |  |     +--rw scaling:trigger                          common:scaling-trigger

     |  |     +--rw scaling:vnf-config-primitive-name-ref?   -> /vnfd:vnfd/df/lcm-operations-configuration/operate-vnf-op-config/day1-2:day1-2/config-primitive/name

```

#### REMOVE_VNF Update

TODO: write the details

REMOVE_VNF operation involves terminating a running VNF instance. This operation could terminate one VNF instance at a time from a NS instance. If termination is invoked for a VNF and it is the last VNF instance in a NS instance, then it cannot be terminated.

The Remove VNF operation currently does not support VNFs that include charms.

### Perform NS Update Operation

osm ns-update  6f0835ba-50cb-4e69-b745-022ea2319b96 --updatetype CHANGE_VNFPKG --config '{changeVnfPackageData: [{vnfInstanceId: "f13dfde9-b7da-4469-a921-1a66923f084c", vnfdId: "7f30ca8b-2c96-4bd3-8eab-b7eb19c2a9ed"}]}' --timeout 300 --wait

```

#### Removing a VNF from UI

- Go to 'NS Instances' on the 'Instances' menu to the left

- Next, in the NS instance where the VNF to be terminated is a part of, click on the 'Action' button.

- From the dropdown actions, click on 'NS Update'

![Remove VNF](assets/500px-NS_Update_Terminate_VNF.png)

- Fill in the form by selecting 'REMOVE_VNF' from the dropdown of 'Update Type' and the member vnf index of the VNF to be terminated and click 'Apply'

- A warning message is displayed, click 'Terminate VNF' to proceed

  - Click 'Cancel' to cancel the termination operation

![Warning message for Terminate VNF](assets/500px-Terminate_VNF.png)

#### Redeploying a VNF from UI

- Go to 'NS Instances' on the 'Instances' menu to the left

- Next to the NS instance which the VNF to be redeployed is a part of, click on the 'Action' button.

- From the dropdown actions, click on 'NS Update'

![NS Update](assets/500px-NS_Update.png)

- Fill in the form by selecting the following,

  - 'CHANGE_VNFPKG' from the dropdown of 'Update Type'

  - The member vnf index of the VNF to be updated

  - VNFDId for the update (Should be same as the vnfd-id of the VNF to be updated)

  - Finally, click 'Apply'

- A warning message is displayed, click 'Redeploy and Update' to proceed

  - Click 'Cancel' to cancel the update operation

![Warning message for Redeploying VNF](assets/500px-NS_Update_Software_Change.png)

## Advanced instantiation: using instantiation parameters

OSM allows the parametrization of NS or NSI upon instantiation (Day-0 and Day-1), so that the user can easily decide on the key parameters of the service without any need of changing the original set of validated packages.