Restore restarts of session services after wizard locale change

This restores functionality removed in the transition to systemd (see commit 4b381c79) and restarts varoius session services which interact with the user via dialogs, notifications or as indicators in order for them to pick up the changed locale.

This fixes #16 (closed).

This is incomplete, the application entries in the shell's launcher plugin are not translated and still use the previous locale (followup on #49 (closed)).