Bug 959142 - Jetpack permanent orange on holly because of reliance on CustomizableUI.jsm import

- Added check for `CustomizableUI` in the UI modules
Fix global 'addon' on trusted content by adding back contentURL to workers, broke from worker detraitification
Merge pull request #1346 from jsantell/959433-fix-worker-addon-global

Fix Bug 959433 Fix global 'addon' on trusted content, r=@erikvold
Merge pull request #1344 from ZER0/holly/959142

Bug 959142 - Jetpack permanent orange on holly because of reliance on CustomizableUI.jsm import r=@erikvold