XD-373 Add 'create tap' shell command

Added '/taps' link to AdminController to represent TapDefinitionResource at XDRuntime
Defined createTap method as SpringXDOperation
Added createTap rest client method at SpringXDClient to invoke TapsController
Added 'createTap' shell cli command to the new class TapCommands
Moved StreamCommands into xd.shell.command package along with TapCommands
Added no-arg constructor for TapDefinitionResource for serialization during REST operation