"Ship-It!" Ships ASCII Art Extension

A Review Board Extension that allows modification to the default "Ship-It!"
message when publishing a review via the "Ship It!" button.

The modifications to original "Ship-It!" text can be anything, as demonstrated
by the ship ascii art currently included by the extension. As currently
implemented, this will include the 'basic' ship, handling rich text reviews as
necessary.

There are a few TODO items, including configurability (to select other ships),
which are all listed in the 'TODO' file.

Testing Done:
Manually tested with different ascii art patterns

Reviewed at https://reviews.reviewboard.org/r/3665/
Remove some useless hooks.

The ship-it ascii art extension had some hooks for a dashboard entry and URLs
that were unused. Get rid of them.
Update RBServerity to use the new JSExtension support.

Review Board 2.0 beta 3 replaced js_model_class with JSExtension. This
is a simple change that updates RBSeverity to use it.

It also switches to using initialize and apply_to.