Support for custom database drivers

[JPDSousa]

At this point Rookit only works with Smof (i.e. MongoDB), through the rookit-mongodb project. It would, however, be interesting to support other database drivers, by generalizing the driver interface.

This issue is related with #3

Planning support for:

• SQLite
• H2
• PostgreSQL

Note: since we are planning to support multiple RDBMSs, it would be cool to investigate integration with Hibernate.

BiStream sources:

• File (done)
• MongoDB's GridFS (in progress)
• Dropbox
• Google Drive
• HDFS

[JPDSousa]

This is currently in progress. The API has been created and the MongoDB adapter is now being built around it.