oox: always save all kinds of 3d effects to the grab bag.

This was actually a bug. It didn't matter much because a document with
an a:sp3d tag but without a:scene3d section would be invalid, but the
code was logically wrong.

Change-Id: Ifa838e425849642c2a1bf6fca6b6a8dc8ed3b465
ooxml: Preserve shape effects when there's more than one

Transformed the preservation process of shape effects to be able to
store more than one effect. For that we:

* Created the Effect struct and added a vector member to the
  EffectProperties struct.
* Changed the shadow effect to use the new Effect struct,
  EffectShadowProperties struct is preserved because the direction
  field still has some use but we should remove it.
* Changed the structure of the grab bag to store more than one effect.
* Modified an existing unit test to check shapes with several effects.

Change-Id: I0dd908fa1d9578827c02ef6272fc9e2b914391be
ooxml: Preserve effects on pictures

If a picture contains some 2D (glow, shadow...) or 3D effect
(rotation, extrusion...), we prevent the importer from transforming
it into a XTextContent so the XShape grab bag is not removed and
the effects are preserved using the existing mechanisms. Added a unit
test for this issue, and modified some existing unit tests to match
the new behaviour.

Change-Id: I3b87069ea208604383a592d34d0a4ceb6b0f9fc7