Adds HALT_ON_ERROR global var for exception handling behavior
Updates tests for new HALT_ON_ERROR. Negative values for Slope, Power and Sat will now clip at 0.0
Updates parse_cc to fix blank metadata, allow either sop or sat to be missing (other must be present)
Updates docs for HALT_ON_ERROR
Updates _sanitize to return empty strings instead of dying.
If ColorCorrection given blank id, set to number of total ColorCorrections
Updates docs with new ColorCorrection.id behavior
Updates tests for parse_cc, fully covered again.