Adds KeyCasr Preferences

Modified osx_defaults to use Shellwords to do proper escaping for the
key and the value (if a string type) of the default being written.  This
way the users of this utility don't have to worry about escaping things
themselves.  This required changing the terminal_preferences to no
longer attempt to excape some of it's keys.

New KeyCastr preferences are:
- Only shows for command keys
- larger font
- Turns off showing preferences on launch
- Hides KeyCastr app from doc (only shows in menu bar)
- Attempts to place in top right corner, though with inconsistent
  results
- Marks it as having been previously launched