More database support

[Khaaz]

Adding support for more Database could be a super interesting features.

Suggestion:
Embeded:

• noSQL embeded? open to suggestion.
  => NeDB - https://github.com/louischatriot/nedb/
• SQLite - package: https://www.npmjs.com/package/sqlite3

NoSQL:
Others NoSQL engine?

• ArangoDB
• RethinkDB

SQL:

• PostGreSQL
• Mysql

All contributions are welcome.
The Database Service just offer an interface with the DB for AxonCore since it uses Database natively.
It needs to replicate the current behavior with a different Database engine.

[Aervyon]

If i may, what is the point of inclduing NeDB? It is very similar to a JSON database.

[Santhosh-Annamalai]

NeDB is a database management solution written in javascript which will be integrated into the application "AxonCore" (since it is an embedded database). So you needn't install standalone databases like MongoDB and use drivers like "MongoDB Node.js driver" for interacting with your database.

NeDB and JSON are highly different because you have to develop methods for doing CRUD operations in a JSON file by yourself. Whereas NeDB has a subset of MongoDB API methods which you'll find very useful and could save a lot of development time and effort. NeDB database is also stored in memory so your application could access data pretty fast (Obviously that won't put a strain in memory resources since data stored in NeDB is quite small usually). You can think of NeDB as SQLite for MongoDB projects. Plus if your data grows over a period of time and when NeDB read / write speeds are insufficient, you can export NeDB data to a MongoDB collection using an utility. Hope it is clear!

[Khaaz]

Updating on this:
Best thing to add would be a support for sequelise which is a SQL ORM that seems pretty powerful.

Obviously any other native support that could be added is also welcome.
Make sure to PR for the dev-v2 branch.