Add and remove constraints from the corpusByMatch assistant

Change-Id: I508312e6c431d0602471eb75fd06e845ffd63631
diff --git a/dev/js/src/vc/fragment.js b/dev/js/src/vc/fragment.js
index 9b87ee2..a623549 100644
--- a/dev/js/src/vc/fragment.js
+++ b/dev/js/src/vc/fragment.js
@@ -9,6 +9,9 @@
 define(['util'], function () {
   "use strict";
 
+  const loc = KorAP.Locale;
+  loc.NEW_CONSTRAINT = loc.NEW_CONSTRAINT || 'New Constraint';
+  
   // Create a VC doc
   function _doc (op) {
     var doc = document.createElement('div');
@@ -91,8 +94,14 @@
         return this._element;
       };
 
+      // Initialize element
       this._element = document.createElement('div');
       this._element.classList.add('vc', 'fragment');
+
+      // Prepend info text
+      this._element.addE('span').addT(loc.NEW_CONSTRAINT + ':');
+      this._frag = this._element.addE('div');
+      
       return this._element;
     },
 
@@ -125,7 +134,8 @@
         root = _doc(this._operands[0]);
       };
 
-      const e = this.element();
+      this.element();
+      const e = this._frag;
       if (l === 0) {
         _removeChildren(e);
       }