Add Check-in capabilities

This only adds check-in capabilities necessary
to implement a check-in UI.

https://bugzilla.gnome.org/show_bug.cgi?id=731113
Add Check-in dialog

https://bugzilla.gnome.org/show_bug.cgi?id=731113
mapBubble: Add Check-in button

https://bugzilla.gnome.org/show_bug.cgi?id=731113
userLocationBubble: Enable Check-in button

https://bugzilla.gnome.org/show_bug.cgi?id=731113