Shapes can contain 3D effects like in the following example:

  <a:sp3d z="488950" extrusionH="63500" contourW="50800"/>

This patch preserves the a:sp3d tag and its attributes using the shape
grab bag and modifies an existing unit test to add this check.

Change-Id: Ice3cae39c71784be0f6c7f2700b07c21a5e1fb6e