VE-1651: Got cart model working + gallery insertion

https://wikia-inc.atlassian.net/browse/VE-1651
VE-1651: Added missing semicolons
VE-1651: Clear cart model when closing the dialog
VE-1651: Addressed some JSCS problems
VE-1651: Adjust layout after gallery fully loaded so focus widget looks ok
VE-1651: Prevent from adding same item into cart twice
VE-1651: Corrected constructor parameter comment
Merge branch 've-sprint-31' into VE-1651

Conflicts:
	extensions/VisualEditor/wikia/modules/ve/ui/dialogs/ve.ui.WikiaSingleMediaDialog.js
VE-1651: Added documentation for ve.dm.WikiaImageCartItem
VE-1651: Add/Remove items from the cart based on the cart model only
VE-1651: Access cart items via getter
Merge branch 've-sprint-31' into VE-1651

Conflicts:
	extensions/VisualEditor/wikia/modules/ve/ui/dialogs/ve.ui.WikiaSingleMediaDialog.js
VE-1651: Addressed CR feedback
Merge pull request #5307 from Wikia/VE-1651

VE-1651: Got cart model working + gallery insertion