API|Resource: Replaced color palette translation map management

Palette translation mapping tables are now handled by ColorPalette.
Each palette has it's own set of translations, each associated with
a unique identifier (string).

Color translations are now defined/updated from game side using the
public Resource API function R_CreateColorPaletteTranslation. The old
method involving updating the DD_TRANSLATIONTABLES_ADDRESS has been
removed.

When the palette's color data is replaced with a table containing a
fewer/greater number of colors -- any existing translation maps will
be cleared automatically (they are no longer valid).

The now unused memory zone purge tag PU_REFRESHTRANS was also removed.

Todo for later: It should no longer be necessary to refer to palette
translations using two-part tmap & tclass identifiers on engine side.