transparency workaround for gazebo default (#12)
transparency workaround for gazebo default (#12)

* use texture_unit alpha_op_ex source1 src_manual src_current 0.1 for transparency in place of ambient and diffuse alphas so transparency works on gazebo default branch as well.

* revert submodule change

* keep ambient and diffuse alpha channels to keep released 7.3.1 working.

osrf/uctf,osrf/uctf,osrf/uctf