Add missing info to 10 minute tutorial

I am new to Activiti and when I followed the 10 minute tutorial I found some seemingly essential (at least for beginners) information missing. Basically nothing tells you that you must use a standalone H2 server, or that your must first create the accountancy group and add fozzie to it.

I couldn't figure out how to build the documentation (ant would get errors about a dependency), so I wasn't able to verify that it looks good once built.