Document 'hex' and 'rgb'

[brandonscript]

IX_STATIC_CONST_STRING kIXToHex = @"hex";                           // [[?:hex]]                                -> String value of RGB ?,?,?,? in hex value.  Last value can be used for alpha otherwise it is 1.0f.
IX_STATIC_CONST_STRING kIXToRGB = @"rgb";                           // [[?:rgb]]                                -> String value of hex string to RGB.

These are now in the source. Should probably be rgbToHex and hexToRGB and need to be documented.