Changes:
* Add sessionToken and pageToken properties to the BOOT action and
update the preview reducer.
Supporting changes:
* Move the mw.popups.createActions to ext.popups/boot.js so that Redux
is used in one file and the actions can be tested in isolation more
easily.
Change-Id: Icd61bf1aeb466899e047432bf9798e2574652830
Reducers as a whole are a WIP, but this implements a baseline from which
to add more.
Changes:
* Create ext.popups.reducers to house all reducers
* Create reducers for preview and renderer state manipulation
* Create rootReducer by combining preview and renderer reducers
* Add QUnit tests for reducers
* Move action types into ext.popups.actionTypes
* Extract rootReducer from boot.js
Change-Id: I8a2296c6846cd4b0552a485e671af1d974944195