Add a "a{sv}" output argument to "AddAndActivate2" D-Bus API.
"AddAndActivate2" replaces "AddAndActivate" with more options.
It also has a dictionary argument to be forward compatible so that we
hopefully won't need an "AddAndActivate3". However, it lacked a similar
output dictionary. Add it for future extensibility. I think this is
really to workaround a shortcoming of D-Bus, which does provide strong
typing and type information about its API, but does not allow to extend
an existing API in a backward compatible manner. So we either resort to
Method(), Method2(), Method3() variants, or a catch-all variant with a
generic "a{sv}" input/output argument.

In libnm, rename "nm_client_add_and_activate_connection_options()" to
"nm_client_add_and_activate_connection2()". I think libnm API should have
an obvious correspondence with D-Bus API. Or stated differently, if
"AddAndActivateOptions" would be a better name, then the D-Bus API should
be renamed. We shoul...