Refactored heavily; added BT.2020 support; added profiling/performace info; autogen tableMode
Heavily refactored to improve readability.
Added BT.2020 support: 4 new modes: "BT.601 to BT.2020", "BT.709 to BT.2020", "BT.2020 to BT.601", "BT.2020 to BT.709".
Added profiling result: why it runs slowly and why it can't be improved significantly. See comments in convertColor()
tableMode is now autogen-ed from modeTable via Moonscript's table comprehensions <3
This is probably the last version unless something major happens