Timeline filtering improvements

Adds new front-end filter options for Community and Public timelines: Show replies, and Show reposts (defaults to true). New filter for Home timeline: Show direct (defaults to false) (fixes #254 (closed)). DMs are already hidden on Community and Public timelines.

I also removed logic that was keeping replies to the current user in the timeline when "show replies" was turned off.

In the future, it would probably be better if this filtering happened on the backend.