feat(filterChanged): pass the changed column as first argument to filterChanged function

When using the filterChanged function, it's now possible to use the first argument - column - to simply do column.filters[0].term to retreive the search term for the column being filtered. This is especially useful if using external filtering.

Closes #4775

Author: caseyjhol

packages/core/src/js/directives/ui-grid-header-cell.js

@@ -237,7 +237,7 @@
                   $scope.col.filters.forEach( function(filter, i) {
                     filterDeregisters.push($scope.$watch('col.filters[' + i + '].term', function(n, o) {
                       if (n !== o) {
-                        uiGridCtrl.grid.api.core.raise.filterChanged();
+                        uiGridCtrl.grid.api.core.raise.filterChanged( $scope.col );
                         uiGridCtrl.grid.api.core.notifyDataChange( uiGridConstants.dataChange.COLUMN );
                         uiGridCtrl.grid.queueGridRefresh();
                       }

packages/saveState/src/js/saveState.js

@@ -587,7 +587,7 @@
                     delete currentCol.filters[index].term;
                   }
                 });
-                grid.api.core.raise.filterChanged();
+                grid.api.core.raise.filterChanged( currentCol );
               }
 
               if ( !!grid.api.pinning && grid.options.savePinning && currentCol.renderContainer !== columnState.pinned ) {