feat(dropdown): new default showonfocus false

As proposed in #1745 (reply in thread) this PR changes the default value for showOnFocus to false.

This will stop the dropdown from opening but allowing it to retain focus and would be better in terms of accessibility (in a manner of speaking)

I don't believe tags normally open when they gain focus (at least with autofocus) anyway (only when the enter key is hit does it open) and using the arrow keys goes through the options without it opening at all. Of course if it is clicked or tapped on, it should open... As this is a breaking change it is supposed to be part of 2.9

Author: lubber-de

src/definitions/modules/dropdown.js

@@ -4005,7 +4005,7 @@ $.fn.dropdown.settings = {
   useLabels              : true,       // whether multiple select should filter currently active selections from choices
   delimiter              : ',',        // when multiselect uses normal <input> the values will be delimited with this character
 
-  showOnFocus            : true,       // show menu on focus
+  showOnFocus            : false,      // show menu on focus
   allowReselection       : false,      // whether current value should trigger callbacks when reselected
   allowTab               : true,       // add tabindex to element
   allowCategorySelection : false,      // allow elements with sub-menus to be selected