Undo/redo hotkeys do not work when focus is on Project, inspector, or action views

The undo/redo hotkeys should only be blocked if keyboard focus is on a text edit control (or another control that has custom handling for undo/redo, but we don't have any of those.

On a related note, the alternate undo hotkey ctrl-shift-Z works while keyboard focus is on timeline text edit box. It should be blocked like regural undo/redo keys.