Geo-replication Usability improvements

[aravindavk]

Feature integration is complete with the issue #271, Opened this issue to track the remaining changes.

• [ ] Non Root Geo-replication
• [ ] XML and JSON Output from CLI
• [ ] Log dir creation (Master and Remote side)
• [ ] Message to show if No Geo-replication sessions in Status output
• [ ] Remote Host field in Status output
• [ ] Rollback functions
• [ ] Other improvements like CLI messages and Log messages
• [ ] Support non default location for .ssh/authorized_keys file
• [ ] SELinux permissions for .ssh/sessions directories(All directories created by Glusterd2 code)
• [ ] Config Set Help
• [ ] API Documentation
• [ ] Files/Directories cleanup after session delete
• [ ] Tests
• [ ] Enhance CLI to accept REST credentials for Remote Cluster(During Geo-rep Create)
• [ ] Already Started/Stopped errors handle
• [ ] Add Brick/Remove brick documentation
• [ ] Validate Remote Volume Format(remotehost::remotevol)
• [ ] Different Error codes to REST APIs failures
• [ ] Different Error codes to CLI failures

@kotreshhr Please add if I missed any items.

[aravindavk]

• [ ] Volume Delete should warn about established Geo-rep sessions or Auto delete established Geo-rep sessions if Stopped
• [ ] Volume stop without force should warn about running Geo-rep session
• [ ] Framework support for showing warning/note after a config is set(For example ignore-deletes)
• [ ] Validations for config items