Shrimp Shader Generator FLTK2 GUI (SVN)

Fixed wrong range in Lafortune model description tag.

Fixed the Ward anisotropic sampling. Cleaned up and hopefully improved a bit the performance of the Ward isotropic, Ashikhmin-Shirley anisotropic sampling, and the Beckmann microfacet distribution.

- add tooltip on filter width s and t with suggested value for each filter type

-Add in file/options an entry for command line to use for the documentation: note the path to the doc is note hard coded(very simple for now)

-little color and layout change of doc

Fixing the mantra dev branch>main branch accidental commit.

Reverted back a couple of changes regarding Mantra addition to renderers. Mantra and VEX work should be committed to the dev branch, _not_ main...

Missing curly braces....

Fixed a problem with the Lafortune model, that was using only results from the last lobe. Added the "pump-up" factor suggested by Attila Neumann to the Lafortune model (defaults to original results with p = 0). Added anisotropy support to the coefficients data. Added 29 materials's coefficients, including data from Tek2Shoot's T2SFilePack for Columbia-Ultrecht CURET BRDF database, and some Cornell Universy Program of Computer Graphics ASTM measurements. Changed the usage information accordingly.
Moved all the data from the main Lafortune XML block to the data header (this will be referenced later for user blocks, to allow the user to create N lobes, and define their characteristics as well).

Added Mantra as a supported renderer (to the respective menu entries and renderers.xml - atm duplicated in data/mantra and data/rib). Added some comments regarding RenderDotC status as well. The VEX tags, vex_include and vex_code are supported already, so initial tests and block+headers porting work can start without "unknown renderer" messages.