Refers #214 -- Form setup for on-desk purchase process
Refers #214 -- Add permission check tests
Refers #214 -- Add purchase detail view
Refers #214 -- Add toggle buttons for purchase state
Refers #214 -- Add ticket update view
Refers #214 -- Add Invoice download
Refers #214 -- Add badge export for ticket and purchase (needs link)
Refers #214 -- Add ticket validation date and add this to the badge exporter
Refers #214 -- Link badge edit/print and purchase print
Fixes #214 -- Add some logging
Refers #214 -- Hide edit and print button on purchase partial during preview
Refers #214 -- Improved table handling
Refers #214 -- Cleanups
Merge branch 'feature/cash-desk' of github.com:EuroPython/djep into feature/cash-desk
Refers #214 -- Pass logo information to the underlying badge generator
Refers #214 -- More intuitive case checking
Refers #214 -- Raise an error if invoice isn't paid

Otherwise the exporter will just output a 0 byte pdf
Merge branch 'develop' into feature/cash-desk

Conflicts:
	pyconde/skins/ep14/templates/base.html
Fixes #214 -- Check permissions for checkin link in menu
Fix inheritance error