Merge fixes from the beta-test into the 2.1.x branch

These fixes include:

 - Accessibility fixes (a11y)
 - Play/pause button issue with screen readers
 - Pause issue when selecting the book that's already playing
 - Pause issue when selecting a chapter that's already playing
 - Fixes that the currently playing book wasn't shown as active

Don't bother about the weird commits - It's because I've merged some redundant commits from `master` into this branch. Note to self: Don't do cherry-picking...