Directory uses PyReconnectLDAPObject and node attributes can be directly
accessed as dictionaries ie node['att_name']
Aspect classes, Dictionary.add() and Node.update() methods added
Adding attribute mapping aspect and fixing older tests
Add python dependencies necessary for jedi to build environment
simplify the nix expression structure for base and dev2.[67].nix
make it easy to install python html documentation

which will be picked up, by pylookup logic in setup-python.el.
add elpy dependency to build environment
Remove epc from base.nix

elpy works without it