feature(cellNav): don't use ENTER as a cellNav if combined with ctrl …

…or alt

  Some editors (like a text area) need to capture ctrl+enter.  Because we are only looking at ENTER in cellNav, the editor was exiting for a cellNav event

src/features/cellnav/js/cellnav.js

@@ -474,7 +474,7 @@
           }
 
           if (evt.keyCode === uiGridConstants.keymap.DOWN ||
-            evt.keyCode === uiGridConstants.keymap.ENTER) {
+            evt.keyCode === uiGridConstants.keymap.ENTER && !(evt.ctrlKey || evt.altKey)) {
             return uiGridCellNavConstants.direction.DOWN;
           }