Merge pull request #647 from est77/master

More travis config cleanup
removed instrumentation added to debug Travis builds.
Added accessors to BSDFSample
Moved SamplingContext to BSDFSample
Removed unused DirectLightingIntegrator constructor
Removed unused file
Removed unused file
Merge pull request #648 from est77/est_bsdf_sample_refactor

BSDF::sample refactor part 2
Use original shading normal for OSL. Added method to update the shading basis
Do not dll-export BSDFSample
Update the ShadingPoint shading basis if needed after sampling the BSDF (OSL)
better tracking of samples/second in the progressive frame renderer.
Merge branch 'master' of github.com:appleseedhq/appleseed
Merge pull request #649 from est77/est_bsdf_sample_refactor

BSDF sampling refactor #3
Merge branch 'master' of github.com:appleseedhq/appleseed
small code cleanups.
Addressed PR comments
Fixed conflicts with master
Small improvements
Merge pull request #650 from est77/est_bsdf_sample_refactor

BSDF sample refactor #4