Fix issue 381, IPersistentCoverTile inherit from plone.directives.form.Schema, every tile interface inherit from IPersistentCoverTile and tiles implements its own interface.
Fix issue 381, IPersistentCoverTile inherit from plone.directives.form.Schema, every tile interface inherit from IPersistentCoverTile and tiles implements its own interface.
Use plone.autoform and plone.supermodel instead of plone.directives
Merge branch 'issue_381' of github.com:collective/collective.cover into issue_381

Conflicts:
	CHANGES.rst
	src/collective/cover/tiles/base.py
Merge branch 'master' into issue_381
Fix imports order
Fix changelog
Add dependency on plone.supermodel
Merge pull request #391 from collective/issue_381

Fix inconsistencies on tiles derivation