CC-5338 : Uncaught SyntaxError: audio resources unavailable for AudioContext construction

creating a single global audio context to avoid resource problems.
CC-5344: Edit Recorded Show -> Rebroadcasts get deleted

When editing a show the record option was getting posted with a false value
even if the value was true. This was caused because on show-edit action the
record form field is disabled
CC-5323: User's Timezone Can Improperly Edit Show
CC-5323: User's Timezone Can Improperly Edit Show
CC-5323: User's Timezone Can Improperly Edit Show

-made localizeDate a static function in ShowFormService
CC-5323: User's Timezone Can Improperly Edit Show

-added comments to timezone getters and setters in Prefences model
 to reduce confusion on station timezone and user timezone
CC-5323: User's Timezone Can Improperly Edit Show

-overlapping show check was using the user's local timezone to compare new
 shows instead of the show's timezone
CC-5323: User's Timezone Can Improperly Edit Show

- fixed to use show's timezone instead of user's timezone when updating a show's
  start and end time after a show has been edited
CC-5323: User's Timezone Can Improperly Edit Show

Edit show from was displaying rebroadcast dates in user's timezone
instead of in the show's timezone
Merge branch 'cc-5232-show-timezone' of dev.sourcefabric.org:airtime into cc-5232-show-timezone