Creates a request series inspector subclass 

This branch:
- Creates a request series inspector subclass to make it easier to use the inspector.
- Removes viewlet support from the viewlet manager.

__To QA__
- Deploy a charm from the charm browser as normal to make sure that it still works.
- Deploy a local charm and use all interactions in the request-series inspector.
- Upgrade the local charm by dragging the same local charm into the canvas again.