resource quota model was separated to 2 models (itacloud-2888)
factory for new model (itacloud-2888)
backup_storage field added to view and serializers (itacloud-2888)
new model usage in createsampledata (itacloud-2888)
test for backup_storage field (itacloud-2888)
Merge branch 'develop' of code.opennodecloud.com:nodeconductor/nodeconductor into feature/itacloud-2888
Make backup calculation more resilient (itacloud-2888)
Merge branch 'feature/itacloud-2888' into 'develop'

Feature/itacloud 2888 (backup_storage in quotas statistics)

Model `ResourceQuota` was separated into 2 models: `ResourceQuota` and `ResourceQuotaUsage`.
Field `backup_storage` was added to this models.
In `ResourceQuotaUsage` `backup_storage` is calculated as Sum ((system_volume_size + disk_volume_size) * sum(max(connected_backup_policies.maximal_number_of_backups, 0)))
`backup_storage` was also added to serializer and stats view.
More fixes for Instance membership refactoring

NC-202
Merge branch 'feature/nc-202' into 'develop'

Instance creation flow fix for CPM refactoring, NC-202
Drop Instance DELETED state

NC-220
Merge branch 'develop' into feature/nc-220
Improve Instance deletion logging, delete instance from DB

NC-220
Merge branch 'feature/nc-220' into 'develop'

Drop DELETED Instance state, NC-220