Cycles Hair: Multiple vertex colours and UV coordinates

Added export of multiple UV coordinates and vertex colour attributes.

A debugging option to export the strands without using the cache has also been removed. 

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54053 954f8c5b-7b00-dc11-b283-0030488c597c