Refactor colors in internal commands

Originally this started as a "deduplicate a bunch of duplicated code in script commands" PR,
but as I was working on that, I discovered there's a lot more that needs to be done than
just deduplication.
Anything which needs a crewmate entity now calls `getcrewmanfromname(name)`, and anything which
just needs the crewmate's color calls `getcolorfromname(name)`. This was done to make sure that
everything works consistently and no copy/pasting is required. Next is the fallback; instead of
giving up and doing various things when it can't find a specific color, it now attempts to treat
the color name as an ID, and if it can't then it returns -1, where each individual command handles
that return value. This means we can keep around AEM -- a bug used in custom levels -- by not
doing anything with the return value if it's -1.

Also, for some reason, there were two `crewcolour` functions, so I stripped out the one in
entityclass and left (and modified) the one in the graphics class, since the graphics class also
has the `crewcolourreal` function.

desktop_version/src/Map.cpp

@@ -2005,7 +2005,7 @@ void mapclass::loadlevel(int rx, int ry)
 			{
 				//A slight varation - she's upside down
 				obj.createentity(249, 62, 18, 16, 0, 18);
-				int j = obj.getcrewman(5);
+				int j = obj.getcrewman(BLUE);
 				if (INBOUNDS_VEC(j, obj.entities))
 				{
 					obj.entities[j].rule = 7;