Add possibility to find value according to a property of the model

I needed that feature to preload existing model objects that are not in the source list.
The comparison is made upon the property setted via the "track by" of the repeater.

Author: JeffGreat

Diff for: src/select.js

@@ -606,6 +606,13 @@
                 for (var p = list.length - 1; p >= 0; p--) {
                   locals[$select.parserResult.itemName] = list[p];
                   result = $select.parserResult.modelMapper(scope, locals);
+                  if($select.parserResult.trackByExp){
+                      var matches = /\.(.+)/.exec($select.parserResult.trackByExp);
+                      if(matches.length>0 && result[matches[1]] == value[matches[1]]){
+                          resultMultiple.unshift(list[p]);
+                          return true;
+                      }
+                  }
                   if (result == value){
                     resultMultiple.unshift(list[p]);
                     return true;