Fix sort operator

* Add server publications for next and previous page
* Add ability to sort ascending or descending

models/usersessiondata.js

@@ -62,6 +62,12 @@ SessionData.attachSchema(
       optional: true,
       blackbox: true,
     },
+    projection: {
+      type: String,
+      optional: true,
+      blackbox: true,
+      defaultValue: {},
+    },
     errorMessages: {
       type: [String],
       optional: true,
@@ -130,6 +136,9 @@ SessionData.helpers({
   getSelector() {
     return SessionData.unpickle(this.selector);
   },
+  getProjection() {
+    return SessionData.unpickle(this.projection);
+  },
 });
 
 SessionData.unpickle = pickle => {