Adding support for "readableBy" and "writableBy" in back

This means that we are now loading maps from server side.

maps/tests/Variables/variables.json

@@ -142,6 +142,29 @@
                  "width":0,
                  "x":88.8149900876127,
                  "y":147.75212636695
+                }, 
+                {
+                 "height":0,
+                 "id":10,
+                 "name":"readableByAdmin",
+                 "point":true,
+                 "properties":[
+                        {
+                         "name":"default",
+                         "type":"bool",
+                         "value":true
+                        }, 
+                        {
+                         "name":"readableBy",
+                         "type":"string",
+                         "value":"admin"
+                        }],
+                 "rotation":0,
+                 "type":"variable",
+                 "visible":true,
+                 "width":0,
+                 "x":182.132122529897,
+                 "y":157.984268082113
                 }],
          "opacity":1,
          "type":"objectgroup",
@@ -150,7 +173,7 @@
          "y":0
         }],
  "nextlayerid":8,
- "nextobjectid":10,
+ "nextobjectid":11,
  "orientation":"orthogonal",
  "properties":[
         {