Drop support for GNOME Shell prio 3.9 (part II).
Perform a real time search.
Switch to an object oriented programming style.

 * RecentEntry class added to represent a recently used file
 * RecentEntryIcon class added to represent the icon for a recently
   used file
 * Functionality of getResultMeta method moved to getResultMetas method
Better names for method parameters.
Add emblems to the icons of the search results.

 * The search results are now showing an emblem of the default
   application, that will be launchend for the given result.