Refactors alarms to decouple them from vnf specific data

Alarms now handle the concept of tags, instead of having vnf specific
parameters in the model. This allows for wider usecases of alarms (e.g. fault management).

Change-Id: I2b395c4bb7f72d4fb7c53b75feccd7de00508013
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>