Remove all remaining GParamSpec name and blurb strings (and fix
indentation while we're there), and add G_PARAM_STATIC_STRINGS to all
paramspecs that were lacking it.
Make all the signals RUN_FIRST instead of RUN_LAST. In particular,
this fixes a crash when creating a new connection and activating the
listbox directly, in which case nmt_newt_listbox_activated() was
running after NmtAddConnection:create_connection() had already quit
the form and unrealized the listbox.