ooxml: Preserve shape 3d effects: material

Shapes 3D effects can specify a material like in the following example:

  <a:sp3d prstMaterial="metal" z="488950" />

This patch preserves the prstMaterial attribute in the sp3d tag using
the shape grab bag and modifies an existing unit test to add this
check.

Change-Id: I7be2dbbcc7e599d5f0fb8fa53ec1d180c18d8ebd
ooxml: Preserve shape 3d effects: extrusion and contour colors

Shapes 3D effects can specify colors for extrusion and contours like
in the following example:

  <a:sp3d extrusionH="25400" prstMaterial="metal">
    <a:extrusionClr>
      <a:schemeClr val="accent5">
        <a:lumMod val="40000"/>
        <a:lumOff val="60000"/>
      </a:schemeClr>
    </a:extrusionClr>
    <a:contourClr>
      <a:srgbClr val="3333FF"/>
    </a:contourClr>
  </a:sp3d>

Colors can be theme-defined or set in RGB and can contain
transformations.

This patch preserves all the color information using the shape grab
bag and modifies an existing unit test to add this check.

Change-Id: Ida168affd4ca2135d0bd8f97135dc1cd1e74165a
oox: Use references to prevent unnecessary object copies

Change-Id: I5113bc581a8ac98b97c6598a5355e050c7ad7860