Hold a reference to OIIO's texture system in ShadingContext.
Changes to support textures in DisneyMaterial.
Merge pull request #493 from est77/ShadingContext_OIIO_textures

Shading context oiio textures
cosmetics.
tweaked comment.
small code cleanups.
all appleseed tools can now load built-in projects.
Saving and loading expression scripts

Buttons handling this operations are found in the middle
between the top widgets and the input are where you can type
the expression.

Buttons are stretched to the whole width of the editor.

Signed-off-by: Marius Avram <marius.avram1309@gmail.com>
fixed performance regression introduced in 36f0961396dfbc393903c5eaadc46cb0ab9a8c43.
Fixing ifndef

The call to the constructor of ShadingContext used in test_bsdfmix.cpp
is valid when both WITH_OSL and WITH_OIIO are not defined, ortherwise
it will result in a compilation problem.

Signed-off-by: Marius Avram <marius.avram1309@gmail.com>
makefluffy now supports include/exclude regexes.
code simplifications.
Merge pull request #498 from marius-avram/oiio_ifdef_bug2

Fixing ifndef
fixed compilation with VS.
code simplifications.
Merge pull request #497 from marius-avram/save_load_script

Saving and loading expression scripts