added new use_shortcut method to shortcuts

this way, you can ask if a particular event will be handled by the
shortcuts system. This takes away the need to special-case many
different possible keys which should be ignored by codemirror by
ignoring them en masse.

IPython/html/static/base/js/keyboard.js

@@ -237,6 +237,12 b' IPython.keyboard = (function (IPython) {'
         return true;
     }
 
+    ShortcutManager.prototype.use_shortcut = function (event) {
+        var shortcut = event_to_shortcut(event);
+        var data = this._shortcuts[shortcut];
+        return !( data === undefined )
+    }
+
     return {
         keycodes : keycodes,
         inv_keycodes : inv_keycodes,

IPython/html/static/notebook/js/cell.js

@@ -169,7 +169,11 b' var IPython = (function (IPython) {'
      */
     Cell.prototype.handle_codemirror_keyevent = function (editor, event) {
         var that = this;
+        var shortcuts = IPython.keyboard_manager.edit_shortcuts;
 
+        // if this is an edit_shortcuts shortcut, we've already handled it.
+        if (shortcuts.use_shortcut(event)) { return true; }
+        
         if (event.keyCode === keycodes.enter && (event.shiftKey || event.ctrlKey || event.altKey)) {
             // Always ignore shift-enter in CodeMirror as we handle it.
             return true;