EntityFramework MongoDB Repository

[tsutomi]

Microsoft is releasing a preview of the support for MongoDB through the Entity Framework.

Currently, the project uses the MongoFramework library to interface MongoDB, but we might want to investigate the possibility of migrating the MongoDB access to that.

Ideally, the only needed library would end up being the Deveel.Repository.EntityFramework, which can potentially be extended with MongoDB-specific functions (if not already supported by EF)