FLOE-113: Implemented the audio metadata panel.
FLOE-113: Replaced tabs in style.css with spaces.
FLOE-113: Fixed the panel flickering issue in the audio metadata panel when switching btw audio attributes.
Merge remote-tracking branch 'cindyli/FLOE-113'

* cindyli/FLOE-113:
  FLOE-113: Fixed the panel flickering issue in the audio metadata panel when switching btw audio attributes.
  FLOE-113: Replaced tabs in style.css with spaces.
  FLOE-113: Implemented the audio metadata panel.
FLOE-115: Completed the captions panel and its unit tests.
Merge branch 'master' into FLOE-115