Store annotations locally

[Ninjani]

Problem

Gooseberry queries Hypothesis for every search and make which is time-consuming and wasteful since many old annotations won't change any more.

Solution

• [x] Store annotations in database
• [x] Use last synced time to check for updates
• [x] Re-implement filtering using all options supported by Hypothesis
• [x] Refactor to only run hypothesis for sync, updating tags, deleting annotations. Everything else should be offline.

Additional context

See issue #75