Better search

[marc-vdm]

TODO

• tests:
  • init search with small test df, see if expected results are returned in expected order
  • add, remove change functions
  • osa_distance() if works correctly
• connect to pdoduct/activity table
• editing of search index (add/remove/change)
• add full query to suggestions

Checklist

• Keep pull requests small so they can be easily reviewed.
• Update the documentation
  • For in-code documentation, please follow the numpy style guide.
  • For user documentation, please update the wiki in
    ./activity_browser/docs/wiki
• Update tests.
• Link this PR to related issues by using closing keywords.

If you have write access (otherwise a maintainer will do this for you):

• Categorize the PR by setting a good title and adding one of the labels:
  bug, feature, ui, change, documentation, breaking, ci
  as they show up in the changelog.
• Add a milestone to the PR (and related issues, if any) for the intended release.
• Request a review from another developer.

[marc-vdm]

@mrvisscher this is now ready for your testing, please see what you think of result sorting, autocomplete and if you manage to get errors somehow.