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