This fixes the fact that the name of the singular type is plural, but
the name of the plural array is singular. Which has always annoyed me,
too. Also this makes it more clear that custom entities don't have much
to do with the editor.
That's what it is - it's an entity in a custom level. Not something to
do with the editor, necessarily. Like before, the name of the XML
element will remain the same.
That's what edlevelclass is... so that's what it should be named. (Also
removes that "ed", too, making this less coupled to the in-game editor.)
Unfortunately, for compatibility reasons, the name of the XML element
will still remain the same.
CustomLevels.h now uses 4-space indents - like all other space-indented
files - instead of 2-space indents. This has bugged me for a while and I
decided to just fix it now.
This is a pretty hefty commit! But essentially, I made a new editorclass
object, and moved all functions and variables that only get used in the
in-game level editor to that class. This cleanly demarcates which things
are in the editor and which things are just general custom level stuff.
Then I fixed up all the callers. I also fixed up some NO_CUSTOM_LEVELS
and NO_EDITOR ifdefs, too, in several places.
As far as I can tell, this function has never been implemented, and only
existed in this header file. FILESYSTEM_getLevelDirFileNames() already
exists (well, used to exist; it's been changed and renamed to
FILESYSTEM_enumerateLevelDirFileNames()), so I'm removing this now.
This accompanies the editor.cpp -> CustomLevels.cpp change; I'll be
splitting out the editor functions in the next commit. The name of the
include guard has been changed as well, but not anything else.
