Add color picker popover.
Refactor Edit menu control. Delegate it to EditMenuManager.
1. Add OperationHelper;
2. Add undo/redo support for shadow type;
3. Refactor applying attributes.
Add Color Picker support;
Refactor Edit menu management;
Update Slide thumbnail management.
Add text color and background color support for text;
Add undo/redo support for colors;
Refactor edit menu item, put it onto the tool bar;
Refactor text undo/redo mechanism.
Change edit menu interface.
Add animate action support to edit menu item.
Refactor animation edit menu..