fg/GUI_IKEv2_advanced_options
Expose the recently added configuration options to GUI.
In the meanwhile:
- update the shared code (will allow to take advantage of nm_utils_parse_inaddr_bin ())
- try to always prepend "@" in the [left,right]id(s): skip just when strictly needed
- propose IKEv2 as default when creating a new IPsec connection via GUI