Add via entries by adding points to RouteQuery

Refactor code so that adding a point to the route query
will add an entry in the sidebar. This allows us to add via
entries from other places than the sidebar module.

https://bugzilla.gnome.org/show_bug.cgi?id=737775
mainWindow: Reveal sidebar when query is updated

https://bugzilla.gnome.org/show_bug.cgi?id=737775
queryPoint: Initialize place property to null

https://bugzilla.gnome.org/show_bug.cgi?id=737775
routeQuery: notify on point added

https://bugzilla.gnome.org/show_bug.cgi?id=737775
routeQuery: Avoid multiple notifies in reset

https://bugzilla.gnome.org/show_bug.cgi?id=737775
Add button template to MapBubble

This adds a template ui to MapBubble with an icon, a content area
and a button area.

The button area contains standard buttons, which bubble sub classes
will opt-in to using the buttons parameter:
    params.buttons = MapBubble.button.ROUTE | ... ;
    this.parent(params);

Bubble sub classes add their own content by:
    this.image.[property] = ...;
    this.content.add(...);

https://bugzilla.gnome.org/show_bug.cgi?id=737775
mapBubble: Add route button

https://bugzilla.gnome.org/show_bug.cgi?id=737775