Updated the kendo music store dashboard docs

Updated the kendo music store dashboard docs with the latest version
Updated SPA docs for music store dashboard.

Updated the "Creating a Single-Page App with KendoUI" document to
reflect the latest code and explain some of the SPA concepts a little
bit more.
Updated main page docs for music store dashboard.
Updates sales page docs for music store dashboard.
Updated music store dashboard screenshots.
Updated dashboard section of Kendo Music Store Intro