[TIDY] Refactor renderlib into two parts

Most of the make scripts only need the schedule part of the renderlib.
The schedule part has way less dependencies (e.g. no ImageMagick), so
those scripts can be used without them now.

archconf2020/__init__.py

@@ -320,7 +320,7 @@ def debug():
 
 def tasks(queue, args, idlist, skiplist):
     # iterate over all events extracted from the schedule xml-export
-    for event in renderlib.events(scheduleUrl):
+    for event in schedulelib.events(scheduleUrl):
         if not (idlist == []):
             if 000000 in idlist:
                 print("skipping id (%s [%s])" % (event["title"], event["id"]))