1. Refactored structure of ComponentCommands.js:
- Fixed indentation.
- Changed order of commands to be a little more organized.
- Explicitly defined MoveCommand variable.

2. Element affected by undo/redo becomes selected.
3. Fixed bug with multiple elements selected after undoing removing an element.
Added unto command for text changes.
Added multiselect ability for slide elements and slide well.
Refactored some of the core files and added a lot of JSDoc comments.