Fixed critical bug EXT-4837 ([NUX] When filter results in null state, provide...

Fixed critical bug EXT-4837 ([NUX] When filter results in null state, provide a message suggesting the user try global search.)

implementation for:
 * Places->My Landmarks
 * My Inventory->My Inventory
 * My Inventory->Recent
 * My Appearance->Wearing
 * My Appearance->My Outfits
updated common text and search url (secondlife:///app/search/all because concrete category without <search_term> is not supported).

 * People/Friends (Common avatar list support can not be used due to accordions)
  * added two strings with help messages into panel_people.xml (one for case when an avatar has no any friends - moved from textbox, another to be shown when there are no friends matching filter)
  * moved logic to show help text into separate method
  * and updated to be used in both cases: friend list is changed, filter is changed.

--HG--
branch : product-engine