1. Moved Volume to separate file
  2. Created IVolume interface and implemented current behaviour in implementation of new interface — VolumeJBOD
  3. Replaced all old volume usages with new VolumeJBOD. Where it is unnecessary to have JBOD — left just IVolume.
  4. Removed old Volume completely
  5. Moved StoragePolicy to separated files
  6. Moved DiskSelector to separated files
  7. Removed DiskSpaceMonitor file

and in "SHOW TABLES" executed in any database with the "Dictionary" engine.

 * "lock_acquire_timeout" controls for how long a query will continue to
acquire each lock on its argument tables
 * "lock_acquire_timeout_for_background_operations" is a per-table
setting for storages of *MergeTree family

* Move some code outside dbms/src folder
* Fix paths

Mass rename: AccessRightsContext -> ContextAccess, QuotaContext -> EnabledQuota, RoleContext -> EnabledRoles, and so on.

Improve access rights: SHOW splitted into SHOW_DATABASES, SHOW_TABLES, SHOW_COLUMNS, SHOW_DICTIONARIES, EXISTS deleted.