contacts: Make DBus-activatable

This commit installs a service file, renames the desktop file
to follow the bus name, and adds the DBusActivatable key to the
desktop file, following
https://wiki.gnome.org/HowDoI/DBusApplicationLaunching

https://bugzilla.gnome.org/show_bug.cgi?id=728266
git: updated ignore
View: moved default value to declarations
ListPane: select the row of the current contact