placeEntry: Add support for plain coordinates

This adds support for parsing plain coordinates with the format
"<latitude>, <longitude>" in PlaceEntry class. When PlaceEntry
detects a valid plain coordinate (valid format, between valid ranges)
being introduced, it will skip the place search, also, no reverse
search is performed.

Plain coordinates places are internally represented by a GeocodePlace
object whose "name" property is null.

https://bugzilla.gnome.org/show_bug.cgi?id=735842
turnPointMarker: Remove custom name

https://bugzilla.gnome.org/show_bug.cgi?id=735842
searchResultMarker: No bubble for unnamed places

https://bugzilla.gnome.org/show_bug.cgi?id=735842
placeEntry: Add parseOnFocusOut option

This fix a usability issue related to plain coordinates support and
sidebar place entries, where user writes a plain coordinate in
the entry and jump to the next entry without pressing INTRO to
confirm the place.

https://bugzilla.gnome.org/show_bug.cgi?id=735842