Remove support for activity fair share scheduling (#1077)

Remove all the code associated to the activity weight fair share
scheduling feature:

- Remove catalogue functions interacting with the ACTIVITY_WEIGHTS table
- Remove code related to activity weights from the scheduler.
- Deprecate and mark as optional objectstore schema fields for activity
  weights (shcema should be backwards and forwards compatible).
- Store only activity information in the drive state. In the catalogue
  methods, default the weight values to 1.0 (avoids having to perform a
backwards incompatible catalogue upgrade)