Add list of saved filters for all data types

[damontecres]

You can now select a saved filter from the server to browse.

This is a pretty big PR due to some refactoring.

FilterListActivity has been rewritten to combine its original purpose and the other list activities.

Activities no longer reuse the tag_activity layout and instead use one more suited.

There's some UI issues though:

1. The width of the dropdown is arbitrary and would be better to calculate it
2. The focus change listener for the dropdown items uses orange instead of the standard blue everywhere else