[mobile] Improve the Flashcard Review buttons layout

[fabd]

From @tbrams via email.

A layout I would vote for would have a button as big as your "Flip Card" button (that is not really needed, since you can just click on the card like you would expect on a mobile phone ^_^), instead of having a tiny button right next to "End".

Issue
Presumably, for mobile users some of the top buttons would be more easily accessible at the bottom of the screen (portrait). If the user often wants to lookup story or dictionary, it would be easier with buttons close to the thumbs? (question marks because I won an iPad and no smartphone >_>)

Considerations

• Story is probably the most often used of the top buttons
• "Exit" at the top is OK because it is secondary, and even better to be out of the way
• If we remove the top button row entirely, we could find some better layout at the bottom

Quick mockup (incomplete)
I did a quick mockup only to realize this won't work when you flip the card but here is some ideas:

• "Flip Card" is a subtle transparent overlay on the card, which actually doesn't do anything because as tbrams mentioned you can tap the card to flip anyway, but it is there as a hint, thus freeing the space at bottom
• we probably want the answer buttons to be bottom-most (unlike this mockup)
• if we move the meta data (strokecount and framenum) somewhere else.. we could use the same overlay idea to overlay "story" and "dict" on to the card..

Tagged discussion for now.

Tagged nice-to-have because it's not critical, but definitely something that is important for mobile users.