Improve search doing LIKE by word rather than by phrases.

[ovidiul]

Moving a code TODO comment from ActionScheduler_Abstract_ListTable.php as an open issue.

It seems that the get_items_query_search method could make use of an improvement to search with LIKE by words, rather than by phrase.

This could complete the search with:

SELECT ... WHERE column LIKE '%this%is%my%phrase%'

as opposed to

SELECT ... WHERE column LIKE '%this is my phrase%'