some entities' item were not properly added to the item registry.
fixed problem introduced in previous commit: the project explorer is empty after the second project load.
switched renderer::Frame's default pixel filter from Mitchell-Netravali to Gaussian.
the path tracing lighting engine's max ray intensity setting is now also applied to all AOVs.
fixed default value for frame pixel format widget, missing in cb1361633203080a33589b6f4b6f2fc0af0ebdc6: "switched default frame pixel format format from 32-bit float to 16-bit float (half)".
in the microfacet BRDF, renamed the mdf_parameter and mdf_parameter_multiplier inputs to glossiness and glossiness_multiplier, and normalized glossiness into [0, 1] for all distribution functions.
Merge branch 'master' of https://github.com/est77/appleseed