Shrimp Shader Generator FLTK2 GUI (SVN)

FIX: array valued variable replacement now works properly

-Add default credits informations to xml and xsl files
-Add <rsl_link></rsl_link> support in the doc system of url for block usage.So just add in each block in the usage section a new element call <rsl_link> it will be transform to a url link.
-Change Lafortune and Fur block usage to support <rsl_link>

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....