UDIM implementation overhaul

[gavinwhelan3d]

Lots of things that could be done to improve UDIM workflow. Here's a few things. 

-better shader for UDIM texture loading. Selecting ":xxxx_basecolor.1001.tga" will load all tiles. No more typing "<UDIM>". 

No more multitile messy set ups. Simple, simple simple. 

- improved display in the Unwrap. Snapping to UDIM tile maybe. just better tools. 

- Better display in the viewport. 

Just improve it please. 

[EricsUsername]

PLEASE ADD: 
Expose RENDER UV TEMPLATE TARGETS to Maxscript. 
(Unwrap_UVW modifier -> UV Editor Window -> Tools Menu -> Render UV Template (dialog then pops into view))
--
The Render UV Template from Unwrap_UVW has  a setting for which UV templates to render. This is set to default and is only changeable via manually drilling to the dialog window. Tiresome/user-energy-expensive.. ESPECIALLY for batching since batching UDIM UV TEMPLATES with MXS isn't possible at this time.

• Choices provided in the dialog window:  #( default , All Tiles, <U1V1>, <U2V1>, <etc>).