some EDFs were still casting indirect lighting when they shouldn't.
fixed slowdown when trying to retrieve the value of absent optional parameters.
fixed build on linux.
fixed build on linux.
radio buttons are now properly styled.
added radio button widget proxy.
added support for ray traced direct lighting in the SPPM lighting engine.
fixed missing direct lighting contributions after glossy/specular bounces in SPPM lighting engine when using ray traced direct lighting.
caustics can now be disabled when using the SPPM lighting engine.
updated devkit sample's project file.
effectively allow using the progressive frame renderer without tile callbacks.
added null tile callback.
added a renderer controller with a per-frame time limit.
Merge remote-tracking branch 'upstream/master'