Add support for MongoDB

[dror-g]

Hi, I'd suggest supporting MongoDB / DocumentDB as they are ~unfortunately~ very popular with developers.

Since it's possible to specify index & columns, it's possible to cross the non-relational divide.

There's a need to use something other than Sqeleton, as it does not support Mongo (and was archived, as well as the new project that took ownership, so maybe seeking alternatives is in the stars regardless..)

Cheers!