mainWindow: use place in search model

Use place instead of location in search model in order to keep
as much information about the search results as possible.

https://bugzilla.gnome.org/show_bug.cgi?id=722102
settings: add recent-places-limit

Add setting to limit the number of recent places to store.

https://bugzilla.gnome.org/show_bug.cgi?id=722102
Add store for recent and favorite places

This patch adds the PlaceStore object that extends GtkListStore.
Recent places can be added to the store and be written to file using
the JSON format.

If adding a recent place exceeds the limit for recent places the
oldest recent place will be removed.

https://bugzilla.gnome.org/show_bug.cgi?id=722102
mainWindow: add storing of recent places

Add recent places visited to the PlaceStore.

https://bugzilla.gnome.org/show_bug.cgi?id=722102
mainWindow: add search completion from PlaceStore

Use the places stored in PlaceStore for popup completion while
searching.

https://bugzilla.gnome.org/show_bug.cgi?id=722102
PlaceStore: add storing of favorites

https://bugzilla.gnome.org/show_bug.cgi?id=722102