Rename edentities to CustomEntity

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.

desktop_version/src/main.cpp

@@ -32,7 +32,7 @@
 scriptclass script;
 
 #ifndef NO_CUSTOM_LEVELS
-std::vector<edentities> edentity;
+std::vector<CustomEntity> edentity;
 customlevelclass cl;
 # ifndef NO_EDITOR
 editorclass ed;