uv pointcloud ql renderproj example minor fix
Volume Retime qL SOP enhancements (see #262)
Volume Retime qL SOP: velocity field name (see #262)
UV QuickShade qL SOP: per-prim assignment switch (see #268)
Attr Visualize qL SOP: added preprocess/split-by-attrib
gallery update: UDIM support
- SOP/Texturing gallery: added "Add UDIM ids" item
- SOP/Visualize: added "SOP: Show UDIM Tiles"

( UDIM Guide:  http://bneall.blogspot.co.nz/p/udim-guide.html )
NEW: udim example hip file (workflow)
UV QuickShade qL SOP: set input as "reference"
Merged work:
- UDIM stuff
- other minor fixes & improvements