Issue browser quick fixes now work.

- Fixed a few bugs in the issue sorting code which resulted in issues getting lost.
- Create a copy of the selected issues list before applying the quickfixes so as to prevent indexing errors when iterating over the issues.
Fixed a crash when pasting brushes.

- When collecting the objects to be selected after the paste, the worldspawn brushes were selected twice, leading to a crash when the brushes are subsequently moved.
Render bounds sizes on top.
Add comparison methods to KeyboardShortcut.
Add hasShortcut method to Action.