spike(services) - introduce services and injected data layer.
spike(services) - update preferences to use BaseService class
spike(services) - create only one instance of EveBackend
spike(services) - rename BaseModel to Resource, move all methods from
Resource to datalayer.py. Renamed endpoint_name to datasource in
BaseService.
Rebase from master, fix item lock and autosave.
Merge pull request #268 from amagdas/spike-services

spike(services) - introduce services and injected data layer.
refactor(users): make users work with citizendesk

make it importable outside of superdesk

SDS-1