Multiple accounts + Charts dashboard

- Adds the possibility to put multiple Google Analytics accounts, not only profiles from a single account
- Adds a graphical dashboard with charts, using the same period navigation menu
- Adds a top bar with the title of the project, as well as a link to switch between table/chart dashboards
- Adds comments about this in the README.md
- See attached screenshot of the charts dashboard

![mpgat graphical dashboard](https://f.cloud.github.com/assets/873209/1546537/ac1aa3ea-4d87-11e3-8278-3ff795d85df2.png)