Re-implement label deletion

This was not ported during v0.9 re-factor.

Fixes #322

client/components/cards/labels.jade

@@ -18,7 +18,7 @@ template(name="editLabelPopup")
   form.edit-label
     +formLabel
     button.primary.wide.left(type="submit") {{_ 'save'}}
-    span.right
+    button.js-delete-label.negate.wide.right {{_ 'delete'}}
 
 template(name="deleteLabelPopup")
   p {{_ "label-delete-pop"}}

models/boards.js

@@ -319,7 +319,7 @@ if (Meteor.isServer) {
       { boardId: doc._id },
       {
         $pull: {
-          labels: removedLabelId,
+          labelIds: removedLabelId,
         },
       },
       { multi: true }