Definitive Edition support and other improvements

[heinezen]

I made a few changes to the openage palette parser that should be useful here too 😄

• Handling of optional fixed alpha values for the palette in line 3: $ALPHA <num>
• Support for comments with # as seen in the modulation_colors.palx palette.
• Empty lines are now skipped
• Splitting with regex because values can have more than one space between them. It previously caused some colour entries containing additional NaNs.
• New getters and setters for the new palette parameters.
• I left the old API intact as-is.

Also, I haven't used Javascript in a while, so I hope I did not introduce some accidental errors.