General code cleanup, convert to ARC.

- Removed all use of dot-syntax for accessors.
- Cleaned up control flow.
- Made formatting more consistent, changed to Unsquared Labs style.

TODO:
- Fix the check for a changed view controller in
  setSelectedViewController:, which is currently wrong because of block
  scope.
- Change unloadedWindowTitle to defaultWindowTitle, use in absense of
  NSToolbarItem identifiers.
- Possibly convert the view controller protocol into a subclass and
  consolidate the interface a bit.
- Convert RHPreferencesTester to ARC (low priority).