[Bf-codereview] Brightness/Contrast Node for Cycles (issue 5564044)

[dfelinto at gmail.com]

Reviewers: bf-codereview_blender.org, brechtvl,

Description:
Contrast helps to adjust IBL (HDR images used for background lighting).

A question, should we call it Bright (as we are doing in composite) or
Brightness in the UI? So far this patch is calling Bright.

Please review this at http://codereview.appspot.com/5564044/

Affected files:
   intern/cycles/app/cycles_xml.cpp
   intern/cycles/blender/blender_shader.cpp
   intern/cycles/kernel/CMakeLists.txt
   intern/cycles/kernel/osl/nodes/CMakeLists.txt
   intern/cycles/kernel/osl/nodes/node_brightness.osl
   intern/cycles/kernel/svm/svm.h
   intern/cycles/kernel/svm/svm_brightness.h
   intern/cycles/kernel/svm/svm_types.h
   intern/cycles/render/nodes.cpp
   intern/cycles/render/nodes.h
   source/blender/blenkernel/BKE_node.h
   source/blender/blenkernel/intern/node.c
   source/blender/makesrna/intern/rna_nodetree_types.h
   source/blender/nodes/CMakeLists.txt
   source/blender/nodes/NOD_shader.h
   source/blender/nodes/shader/nodes/node_shader_brightness.c
   source/blender/nodes/shader/nodes/node_shader_gamma.c