INT-2981 (S)FTP Change Commands, Options to Enums
INT-2981 Add Support For 'mv' To File/Remote/GW
INT-2981 (S)FTP Namespace Support and Docs
INT-2981 Create Remote Dirs if Needed
INT-2981 Add 'mv' Command to What's New
INT-2981 Polishing - PR Comments

Add javadocs to enums.

Polish schemas to use an enumerated type for available
gateway commands.