Valera/captions keyboard access 2

Several improvement of Video Alpha controls for people with disabilities.

1.) All controls are now labeled with title attributes. Screen readers will announce them properly.
2.) You can tab through all of the controls in succession, including the captions panel.
3.) qTip tooltips have been removed. No more accidental clicking on a wrongly placed qTip tooltip with no effect to the actual control.
4.) Each control is now highlighted when it is in focus (Tab key, mouse click, mouse hover, click).

This PR relates to the tickets

1.) https://edx-wiki.atlassian.net/browse/BLD-214
2.) https://edx-wiki.atlassian.net/browse/BLD-170

@polesye and @dmitchell please review.