Add version command

- Adds /version (with /ver as an alias)
- Adds 'spout.command.version' permission to the 'version' command.
- Adds 'spout.command.batch' permission to the 'batch' command.
- Fixes the 'validate_input' command not being registered on startup.
- Changes the server version output displayed on startup.

Signed-off-by: Steven Downer <grinch@outlook.com>