Adds authentication checks and filtering for relations
Merge pull request #70 from granoproject/relperms

Adds authentication checks and filtering for relations
pep8 the schema logic.
Fix relation permission queries - failed here.
pep8 attribute and pipeline model.
Support arbitrary metadata on schemata via a `meta` dict.
Merge branch 'master' into images

Conflicts:
	grano/logic/schemata.py