Spherical panoramic head - remixed

This is a remix of the panoramic head by BlacklightShaman. It is a very nice design - I especially like the quick release mount. I added a few mods to make it easier to use with my setup. These are as follows:

Horizontal arm:

- added alignment marks around the pivot point at 30 degree intervals
- made a cavity in the bolt area to accept/capture a nut for a 1/4" dia. x 20 bolt
- made a hole under the bubble level cavity so you can use a thin rod or drill bit to push the bubble level back out if you want to remove it.

Vertical arm:

- added alignment marks around the pivot point at 90 degrees

Transversal arm:

- added alignment marks around the pivot point at 30 degrees
- lengthened the quickmount plate bolt channel to allow the plate to slide further back
- added a groove past the end of the channel to allow for the quickmount cam bolt protrusion
- added a small hole past the M5 nut pocket in the pivot area to allow use of a small rod or drill bit to remove the n