Add count of exclusively covered digests to each ignore rule

golden/frontend/res/imp/ignores-page-sk.html

 <!--
    The <ignores-page-sk> custom element declaration.
 
   A container element to manage the any digests that should be ignored.
 
   Attributes:
     None
 
   Methods:
     pageSelected: This function has to be called if the page is selected
@@ skipping 32 matching lines @@
 
       .ignoresPageWrapper {
         padding: 1em;
       }
 
       #nameHeader,
       #updatedByHeader,
       #expiresHeader,
       #queryHeader,
       #noteHeader,
-      #countHeader {
+      #countHeader,
+      #exCountHeader {
         display: inline-block;
         font-weight: bold;
         margin-right: 0.5em;
       }
 
       #nameHeader {
         width: 15em;
       }
 
       #updatedByHeader {
         width: 15em;
       }
 
       #expiresHeader {
         width: 10em;
       }
 
-      #countHeader {
+      #countHeader,
+      #exCountHeader  {
         width: 6em;
       }
 
       #queryHeader {
         width: 20em;
       }
 
       #noteHeader {
         width: 20em;
       }
@@ skipping 34 matching lines @@
 
     </style>
     <div class="layout vertical ignoresPageWrapper">
       <div class="layout horizontal">
         <div id=nameHeader>Name</div>
         <div id=expiresHeader>Expires</div>
         <div id=updatedByHeader>Updated By</div>
         <div id=queryHeader>Filter</div>
         <div id=noteHeader>Note</div>
         <div id=countHeader>Ignored</div>
+        <div id=exCountHeader>Exclusive</div>

[mtklein, 2016/08/05 21:37:57]

Exclusively ignored?
Ignored by only this rule?

[stephana, 2016/08/08 15:13:53]

I don't think there is a good wording for the header alone. 
So I collapsed the two values into one column and added a tooltip to the header.

See

https://screenshot.googleplex.com/T3RsDzSjz10.png

       </div>
       <div id=summaries class="vertical layout">
         <template is="dom-repeat" items={{ignores}}>
           <ignore-summary-sk value="{{item}}"></ignore-summary-sk>
         </template>
       </div>
     </div>
 
     <paper-dialog id="confirmDelete">
       <h2>Confirm Delete</h2>
@@ skipping 147 matching lines @@
       },
 
       _openDialog: function(isEdit) {
         this._isEdit = isEdit;
         this._readyToAdd();
         this.$.addEditDialog.open();
       }
     });
   </script>
 </dom-module>