Liberate --notes type enhancements

[rbielaws]

There are a couple, hopefully super simple things that would seriously enhance usability. And a couple more that would be seriously cool.

After legacy downloads, books and PDFs are likely pulled down the day one adds them to their library. Bookmarks mostly happen later. This makes the need to update them more likely than audio or PDF but...

Currently, to update them you must manually select each book and explicitly request bookmarks, but the default location when manually saving isn't the same place as bookmarks retrieved during book download and perhaps the format isn't either. So replacing any existing file with it's update is cumbersome.

Here are a few key points that that beg enhancement.

1. Make the directory where automatic bookmark saving would typically happen, the default when saving from the 'View clips and bookmarks' dialog. I realize, if the book hasn't been downloaded, the directory may not exist and the current root value is the most reasonable fallback but that scenario is probably atypical.
2. It seems to make good sense for the default export format on that dialog to match the configured automatic format too.
3. As the pinnacle of convenience, since Listening History is probably not available as the basis of something really nice, adding a "Set bookmarks download status" similar to that available for Audio and PDF would greatly enhance usability.
4. Wait! That's not the true pinnacle. An option to merge bookmarks into the .cue file would seriously be COOOOL. Whatever you used to play your book would have your bookmarks already loaded. I'm not sure how messy this would be to support users who want a chapter per file but I don't do that so if you can't support them I'm ok with saying too bad ;-D