various changes: irods interaction, metadata store

Initial implementation of interaction with irods,
mainly in storage.py. This should also define our interface,
but is not final yet.
Implements listing and creating directories.
I've been looking closely at stoxy and what we develop here should
be easily adaptable.
Interaction with the rest of the code is in auth.py and routes.py

metadata store: invenio client and metadatastore. Both still
incomplete and will surely change a lot.
I will also (and first) implement a metadata connection to irods.

Sorry for this messed up commit.