Moves keycaster under sprout-osx-apps
Adds shim from old pivotal_workstation location

Also updates the location of the included addloginitem recipe
Adds KeyCastr Preferences

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