Improvements
- Backend changes for UpdateSource model
- `fetch_method`: Specifying fetch method (one of 'POST', 'GET', 'GIT')
- `enabled`: Is the source active for periodic fetching?
- `override_classification`: Should the classification assigned to the source override what's defined by the signature
- `configuration`: Processing configuration that's specific to the source
- `update_interval`: The update check interval for the specific source (default is the global `update_interval_seconds`)
- `ignore_cache`: Ignore caching (ie. force updater to always fetch from remote source)
- Frontend changes:
- Update UpdateSource dialog into a two tab design ("General", "Network")