Vue Comments: Comments ported to Vue + DnD fileupload

* Drag and drop files to comment editor to add a file attachment
* Using Vue to render comments

Since comments now has attachments we need to update the schemas
./manage.py maintenance replace_pillar_node_type_schemas

src/scripts/js/es6/common/vuecomponents/mixins/UnitOfWorkTracker.js

@@ -0,0 +1,59 @@
+/**
+ * Vue helper mixin to keep track if work is in progress or not.
+ * Example use:
+ *      Keep track of work in own component:
+ *          this.unitOfWork(
+ *              thenDostuff()
+ *                  .then(...)
+ *                  .fail(...)
+ *          );
+ * 
+ *      Keep track of work in child components:
+ *          <myChild
+ *              @unit-of-work="childUnitOfWork"
+ *          />
+ * 
+ *      Use the information to enable class:
+ *      <div :class="{disabled: 'isBusyWorking'}">
+ */
+var UnitOfWorkTracker = {
+    data() {
+        return {
+            unitOfWorkCounter: 0,
+        } 
+    },
+    computed: {
+        isBusyWorking() {
+            if(this.unitOfWorkCounter < 0) {
+                console.error('UnitOfWork missmatch!')
+            }
+            return this.unitOfWorkCounter > 0;
+        }
+    },
+    watch: {
+        isBusyWorking(isBusy) {
+            if(isBusy) {
+                this.$emit('unit-of-work', 1);
+            } else {
+                this.$emit('unit-of-work', -1);
+            }
+        }
+    },
+    methods: {
+        unitOfWork(promise) {
+            this.unitOfWorkBegin();
+            return promise.always(this.unitOfWorkDone);
+        },
+        unitOfWorkBegin() {
+            this.unitOfWorkCounter++;
+        },
+        unitOfWorkDone() {
+            this.unitOfWorkCounter--;
+        },
+        childUnitOfWork(direction) {
+            this.unitOfWorkCounter += direction;
+        }
+    }
+}
+
+export { UnitOfWorkTracker }