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

Implemented passing of entered filter substring without head spaces to search URI in help message for null filtered results.
* Updated setting "no item message" to use search term from filter editor for avatar & group lists and for inventory panels.
* Updated appropriate translatable strings to get [SEARCH_TERM] substitution.
* Updated processing of filter substring to pass original string to methods applied new filter.

Additional necessary changes
* Changed place to set "no item message" for group list from refresh to where filter is updated (like in avatar lists)
* Removed converting of filter substring to upper case in Places & My Appearance sidepanels (this conversion has already been implemented in where filter is applied)
* Added a separate message for Landmarks to set search URI to secondlife:///app/search/places for Lanmarks panel;
 other inventory related panels have URL to all searched categories (secondlife:///app/search/all)

Reviewed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/326/

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branch : product-engine