Resolve "Ability to mark Podcast episode as played"
This PR contains a couple of commits:
- 6c6ea2f7: Marks the currently selected set of entries as already played by setting the play count to 1, if and only if current play count is 0 ('Never'). Closes #1463.
The other commits are just drive-by-commits:
- white space fixes
- documentation updates
- some files added to.gitignore