2.5.x features

shows, show-schedules, show-preview, show-history-feed, item-history-feed endpoints to the HTTP api to be used via NewscoopAirtimePlugin

These endpoints are needed for airtime pro instances and should be merged to saas branch.
``` php
$ccShow = CcShowQuery::create()->findPK($this->_showId);
$info = $ccShow->toArray(BasePeer::TYPE_FIELDNAME);
```
works fine for me (testing off of your version of 2.5.x-features).
Also, why are there 2 separate code paths for /shows (when the user passes a show_id vs when they don't)?
These should probably use the same code so that any filtering or other operations on the data don't need to be duplicated.

In fact, after looking at it, the Show class is entirely foolish right now. It should be rewritten to provide a singleton CcShow object rather than just an ID... every single function in the class is making an unnecessary database call.