Add indexer service (equivalent of Dereferencer, but named more accurately)

spec/javascripts/unit/admin/services/indexer_spec.js.coffee

@@ -0,0 +1,13 @@
+describe "indexer", ->
+  Indexer = null
+
+  beforeEach ->
+    module "ofn.admin"
+
+  beforeEach inject (_Indexer_) ->
+    Indexer = _Indexer_
+
+  it "indexes an array of objects by id", ->
+    objects = [{id: 1, name: 'one'}, {id: 2, name: 'two'}]
+    index = Indexer.index objects
+    expect(index).toEqual({1: {id: 1, name: 'one'}, 2: {id: 2, name: 'two'}})