Tbodysort widget enhancement. (#1312)

* Enhancement/LockTbodyHeader

Added two new variables to hold the lockhead option and the head row class (defined in cssHeader).
If the new widget option 'sortTbody_lockHead' is true, the header row will be moved back to the top of the <tbody> after sorting, this is intended to be used with the 'sortTbody_sortRows' option set to true.
This will allow the <tbody> and it's child rows to be sorted while keeping the header row at the top of the <tbody>.

* The new lockHead option now used the `sortTbody_primaryRow` value instead of the `cssHeader` value.
This means the new widget option can be used out-of-the-box, meaning the user won't need to change any default parameters in the js files.

* Changed setting to test old code.

* Roll back to master version.

* Widget sortTbodies
  - Removed `lockHead` var since it's only used once
  - Ammended `sortEnd` condition

js/widgets/widget-sortTbodies.js

@@ -1,6 +1,7 @@
-/*! tablesorter tbody sorting widget (BETA) - 11/22/2015 (v2.24.6)
+/*! tablesorter tbody sorting widget (BETA) - 11/07/2016 (v2.24.7)
  * Requires tablesorter v2.22.2+ and jQuery 1.4+
  * by Rob Garrison
+ * Contributors: Chris Rogers
  */
 /*jshint browser:true, jquery:true, unused:false */
 /*global jQuery: false */
@@ -38,6 +39,16 @@
 					// find parsers for each column
 					ts.sortTbodies.setTbodies( c, wo );
 					ts.updateCache( c, null, c.$tbodies );
+				})
+				.bind('sortEnd', function() {
+					// Moves the head row back to the top of the tbody
+					var primaryRow = wo.sortTbody_primaryRow;
+
+					if ( wo.sortTbody_lockHead && primaryRow ) {
+						c.$table.find( primaryRow ).each( function(){
+							$( this ).parents( 'tbody' ).prepend( this );
+						});
+					}
 				});
 
 			// detect parsers - in case the table contains only info-only tbodies