Initial commit of RavenDb provider.
Created sample using RavenDb, using a copy of SingleTenantWebApp.
Add RavenDb project to MR solution.
Add RavenDb sample to Samples solution.
Merge branch 'master' into RavenDbProvider
changes i had to make to get raven working
rename classes to Raven*; implement Get for GroupRepo
change to use new names for raven DB
slight change to event source API
slight change to event source API