MainWindow: Minor indentation fixes

https://bugzilla.gnome.org/show_bug.cgi?id=706726
MapView: Separate showNGotoLocation method

MapView now provides a separate method for showing a location and
going to it while retaining the showLocation for only showing the
location on the map.

https://bugzilla.gnome.org/show_bug.cgi?id=706726
Add a context menu

Currently this menu has only one item: "What's here?". If user activates
this item, a reverse geocoding is performed for the coordinates where
user right clicked and place information (currently only the name) is
shown in bubble (just like for forward geocoding search results).

Next would be to add a "I'm here" menu item to provide user the ability
to correct (or improve the accuracy) of his/her location.

https://bugzilla.gnome.org/show_bug.cgi?id=706726
MapView: Make Geoclue property public

https://bugzilla.gnome.org/show_bug.cgi?id=706726
Geoclue: Allow overriding location

Currently this only updates the concept of user location within Maps.

I'm hoping that later we can build something more sophisticed on top of
this: Allowing user to easily submit WiFi/IP information to server to
not only improve geolocation for the user submitting the data but also
other users (when) in the same area. This will be very important since
the open/free geolocation services we (will) use in geoclue don't have
enough coverage/accuracy.

Perhaps geoclue can provide an API for data submission:

https://bugs.freedesktop.org/show_bug.cgi?id=68536

https://bugzilla.gnome.org/show_bug.cgi?id=706726
ContextMenu: Add 'I am here!' menu item

When launched, it overrides Maps's concept of user location. We also do
a reverse geocoding to set a proper name on the user location pin.

https://bugzilla.gnome.org/show_bug.cgi?id=706726
geoclue: Make findLocation() public

https://bugzilla.gnome.org/show_bug.cgi?id=706726
MainWindow: Remove some dead code

https://bugzilla.gnome.org/show_bug.cgi?id=706726
MainWindow: Allow switching back to auto location

After user him/herself overrides location, allow him/her to switch back
to automatic location detection through geoclue. We do this through the
'Goto my location' button.

https://bugzilla.gnome.org/show_bug.cgi?id=706726