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.