Cleanup.

Get rid of duplicate color definition, and use a single TextView for
repo owner and repo name. The latter also improves line break behaviour.
Improve commit header layout.

Fix margins of change summary and make the commit title stand out a
little more.
Improve issue header layout.

Make margins and text size consistent to what is used elsewhere, and
remove margin under comment header (the list view items have their own
padding).
Print comment count in pull requests as well.
Bold actor names in headers.
Make release header look less crammed.
Fix a number of inspection warnings.