Add ability to enable/disable maintenance mode from cli.
Changed class name to mode
Use OC\Config instead of OC_Config
Merge pull request #8748 from owncloud/cli_maintenance_mode

Add ability to enable/disable maintenance mode from cli.

* owncloud/cli_maintenance_mode:
  Use OC\Config instead of OC_Config
  Changed class name to mode
  Add ability to enable/disable maintenance mode from cli.