Added multiselect ability for slide elements and slide well.
Element affected by undo/redo becomes selected.
Fixed bug with multiple elements selected after undoing removing an element.
Lot of refactoring:
- Fixed indentation.
- Changed order of commands to be a little more organized.
- Removed 'return' where it's not needed.
- Added 'this' variable in forEach calls.
- Fixed explicitly defined variables where seen.
Added unto command for text changes.
Cleanup
Merge branch 'multiselect'

Conflicts:
	app/bundles/app/strut.deck/Deck.js
	app/bundles/app/strut.deck/Slide.js
	app/bundles/app/strut.slide_components/view/ComponentView.js
	app/bundles/app/strut.slide_snapshot/SlideSnapshot.js
	app/bundles/app/strut.themes/ClassEditor.js
	app/bundles/common/tantaman.web.undo_support/CmdList.js