add OCIO shaper transforms
move AP1 definition into Utilities_Color with AP0 and the other pre-defined primary sets
add AP0-to-AP1 matrix and AP1-to-AP0 matrix into README-MATRIX
add ACEScg transforms
update ARRI Alexa IDT-generation scripts and rename ARRI Alexa IDTs
fix a missing import statement
make separate reference implementation transforms for verifying 10- and 12-bit ACESproxy
add a clamp to prevent values over HALF_MAX in the ACEScc to ACES conversion

#48
fix a typo in ACEScg transforms

transform output was returning the R channel in RGB
change default output range for video odts to full range instead of SMPTE legal range
add Rec709 D60 sim for dim surround; add desaturation into Rec709 D60 sim for dark surround
remove dark surround rec709 odt
simplify OCIO shapers
update ACEScc transforms to reflect latest version of document
update ARRI Alexa IDT-generation scripts and rename ARRI Alexa IDTs to add <ACEStransformID> and <ACESuserName> tags
add <ACEStransformID> and <ACESuserName> tags to ACEScc, ACEScg, ACESproxy, and Sony IDTs
add <ACEStransformID> and <ACESuserName> tags to LMTs, DCDM ODTs, and HDR_PQ ODTs
add <ACEStransformID> and <ACESuserName> tags to remaining transforms