Make filters caseless by default

Fuck it.

closes #187
closes #190
Merge branch 'master' into main-widget
InlineMediaDownloader: Close the streams

We were leaking the fds from *all* the media, up to 3 of them per image.

This fixes #235 for me.
sidebar: switch to GtkBox
TweetListEntry: connect retweet_cb
timelines: Add inline progress display row
MainWindow: Remove progress indication API