only one level in subrelation-tree

* in the subrelation list only one (current) level of child relations
  is displayed. The next level appears, once a subrelation is
  selected. That way one can easily navigate through the relation tree.
* the list of parent relations only shows the next parent
  (without this change all parents in the tree were displayed)

This was the behaviour before the sqlalchemy port. See also #65.

api/details.py

@@ -190,9 +190,9 @@ def _hierarchy_list(self, rid, subs):
         h = mapdb.tables.hierarchy.data
 
         if subs:
-            w = sa.select([h.c.child], distinct=True).where(h.c.parent == rid)
+            w = sa.select([h.c.child], distinct=True).where(h.c.parent == rid).where(h.c.depth == 2)
         else:
-            w = sa.select([h.c.parent], distinct=True).where(h.c.child == rid)
+            w = sa.select([h.c.parent], distinct=True).where(h.c.child == rid).where(h.c.depth == 2)
 
         sections = sa.select([r.c.id, r.c.name, r.c.intnames,
                               r.c[self.level_column].label('level')])\