Add state for navigation

Currently selected navigation item is available under the navigation
variable so that the whole application has access to it.

app/reducers/contextMenu.jsx

@@ -1,13 +1,12 @@
 import { UPDATE_CONTEXT_MENU, OPEN_CONTEXT_MENU, CLOSE_CONTEXT_MENU } from '../constants/contextMenu'
 
 
-const initialState =
-  {
+const initialState = {
     opened: false,
     x: 0,
     y: 0,
     items: []
-  }
+}
 
 export default function contextMenu(state = initialState, action){
     switch (action.type) {

app/reducers/index.jsx

@@ -1,8 +1,10 @@
 import { combineReducers } from 'redux'
 import contextMenu from './contextMenu'
+import navigation from './navigation'
 
 const rootReducer = combineReducers({
-  contextMenu
+    contextMenu,
+    navigation
 })
 
 export default rootReducer

app/reducers/navigation.jsx

@@ -0,0 +1,18 @@
+import { UPDATE_SELECTION } from '../constants/navigation'
+
+const initialState =
+{
+    selection: {
+    }
+}
+
+export default function navigation(state = initialState, action){
+    switch (action.type) {
+        case UPDATE_SELECTION:
+            return Object.assign({}, state, {
+                selection: action.selection
+            })
+        default:
+            return state
+    }
+}