Adding an charm generator

Current version only supports Ansible.

It takes as input an empty charm with playbooks and generates
the following files:
- metadata.yaml
- layers.yaml
- reactive/<ansible_charm>.py
- actions.yaml
- actions/<action-name>

After that, it is only required to build the charm.

NOTE: In this version, it doesn't support parameters yet.

Change-Id: Ia771185a38421a04c1adcef4ded3d7a55fa164ee
Signed-off-by: Eduardo Sousa <esousa@whitestack.com>