Revert "Collection Editor based on patch by Julian Eisel"

This reverts commit 3da834e83c.

We will use the outliner for this now.

I'm also moving the collections_ops.c to outliner_collections.c

source/blender/python/intern/bpy_rna_callback.c

@@ -174,7 +174,6 @@ static eSpace_Type rna_Space_refine_reverse(StructRNA *srna)
 	if (srna == &RNA_SpaceConsole)          return SPACE_CONSOLE;
 	if (srna == &RNA_SpaceUserPreferences)  return SPACE_USERPREF;
 	if (srna == &RNA_SpaceClipEditor)       return SPACE_CLIP;
-	if (srna == &RNA_SpaceCollectionManager)     return SPACE_COLLECTIONS;
 	return SPACE_EMPTY;
 }