Search improvements

[kamtschatka]

Creating a PR to show off the current state. This is definitely not something to merge.

Things that are still missing:

• Adding pagination to the search --> i have no idea why I can't use the Bookmarks component with a query there, it complains about the Ref
• UI for simple search queries: I can definitely not manage that^^
• Lots and lots of tests

What I have done:

• Added a grammar for advanced search
• Added different expressions that can be combined
• Added documentation
• Replaced the existing bookmark search with the new expressions and added pagination. Seems to work fine --> needs tests
• Replaced the search with the new experssions --> also needs tests. Pagination should also work
• Migrated the db to have a bookmark type column
• Compared the performance of the existing searches with the new mechanism: There is more to do in memory, so there is overhead, but with ~5000 bookmarks the difference is e.g. 20ms before and 60ms after. I have an idea on how to optimize that, but right now, I don't think that it is very important.