Blender Git Loki

Added some backward compatibility with old yafray blendershader. Because of missing
parameters the material preset menu won't be as useful. Both glass presets will look the same
because there is no 'filter' parameter in the old yafray for instance.
So using the new Blender version with an old yafray version should work a bit better,
though the other way around, using the new yafray with an old blender version, will generally
not work as well.

I added a few extra things. In 'yafray' panel re-arranged some buttons, and added a new
button 'Clamp RGB'. This button will be enabled by default and helps to improve AA on
high contrast edges in the image. When using bokeh however, it is best to switch this off,
otherwise lens shaped highlights will be quite a bit less visible.

Changed the 'extinction' parameter name to the probably more correct term 'absorption',
though mathematically it works out the same. Also changed the behaviour of this color,
it no longer specifies a color that will be removed as I wrote in the previous commit,
but instead the actual color at one (blender) unit of distance. The 'Ds' (distance scale)
button below the color sliders controls the scaling of this unit distance.
What this means is that if you take the standard blender cube, which covers two units of
distance by default, setting the distance scale button to 2.0 will make sure that the color
you specified is exactly that color at that distance (provided the base color itself is white
of course, or 'filter' is 0, otherwise it will be filtered by the base color too).
Beyond this distance the color will get darker.

The glow option for point/soft/sphere lights has a new parameter 'GloOfs', or glow offset.
Setting this to a higher value then 0 will soften the central peak of the glow.

Another unreported bug fix: For xml export, when yafray failed to render the xml file
for some unknown reason, or because of other problems, the export code would still load
the previously rendered image, this causes problems however if the image resolution is
not the same as the current Blender buffer, and so could cause memory corruption or crashes.
This is now taken into account.

World image backgrounds now use the blender mapping settings as well, but only the
'AngMap', 'Sphere' and 'Tube' settings. But in yafray those last two, unlike Blender, cover
the whole view, not just the upper half, so is not really fully compatible with yafray.
So now you have to set one of these buttons too when loading a hdr lightprobe image.
btw, something I forgot to mention in previous commits is that the exposure control using
the texture brightness slider is no longer restricted to integer values. It is now a
floating point value, so you're not restricted to the 0 1 and 2 slider positions anymore,
anything in between will work too.

And finally, display updating is now more like Blender, using the mouse cursor as frame
counter for animation, etc.