feat(dropdown): onSearch callback

This PR adds a new onSearch callback to allow access to the search term being entered so that external processes can be informed about the term being typed in. Such processes may include an API that requires authentication with a token, especially if the website in question already has an existing API

Author: jamessampford

src/definitions/modules/dropdown.js

@@ -297,7 +297,9 @@ $.fn.dropdown = function(parameters) {
             : module.get.query()
           ;
           module.verbose('Searching for query', query);
-          if(module.has.minCharacters(query)) {
+          if(settings.fireOnInit === false && module.is.initialLoad()) {
+            module.verbose('Skipping callback on initial load', settings.onSearch);
+          } else if(module.has.minCharacters(query) && settings.onSearch.call(element, query) !== false) {
             module.filter(query);
           }
           else {
@@ -4038,6 +4040,7 @@ $.fn.dropdown.settings = {
   onChange      : function(value, text, $selected){},
   onAdd         : function(value, text, $selected){},
   onRemove      : function(value, text, $selected){},
+  onSearch      : function(searchTerm){},
 
   onLabelSelect : function($selectedLabels){},
   onLabelCreate : function(value, text) { return $(this); },