Camera options in shape 3D effects can have rotation settings like in
the following example:

  <a:camera prst="perspectiveRelaxedModerately" zoom="150000">
     <a:rot lat="19490639" lon="0" rev="12900001"/>
  </a:camera>

This patch preserves the a:rot tag and its attributes using the
shape grab bag. We created the class Scene3DRotationPropertiesContext
to be piled on top of a Scene3DPropertiesContext and process the
contents of the child item. It also adds a unit test for this case.

Change-Id: Id6bf58ad05fe5b49061619b6750ed0658badc9af