Implement Internal DataSources

Internal DataSources must be able to be managed in the same way as external DataSources - i.e. they should be the same model or one which inherits from DataSource.

We need to support 3 distinct types of internal source:

• SQL (harder)
  • Need to be able to define table structure
  • PUT / POST one or multiple row(s) at a time
• NoSQL / MongoDB (easier)
  • Documents can just be pushed once collection has been created
  • PUT / POST one or multiple document(s) at a time
• CSV (easier)
  • Just a file
  • Don't need to handle updates