Naive DB + Rocksdb implemenation

[GregTheGreek]

This pr introduces a naive implementation of the database traits (read & write), and an implementation of rocksdb. Something to note about database implementations in rust is that they're built with lifetimes, thus they will always close, there is no need to gracefully shut them down.

Discussion points:

• DatabaseService trait is currently commented out since I ran into sizing issues return Self open to discussions on how to solve that. The implementation has Open()
• Research on leveldb showed that its fairly unmaintained and using old Rust idioms.
• How do we handle reads that return no result? Check out RocksDb::read or RocksDb::bulk_read

Closes #110

[austinabell]

:D would be nice to have an in memory db for testing purposes, so I will open an issue to add this after (I can do this as I know how it can be done, but could leave if someone else wants to do)

[austinabell]

Meant to approve before, but lgtm once #136 comes in to fix the CI

Edit: Review still valid

[ec2]

License. Otherwise lgtm

[ec2]

REMEMBER LICENSE

[dutterbutter]

@GregTheGreek I think we should reference the db in the chain_store

[GregTheGreek]

@GregTheGreek I think we should reference the db in the chain_store

What do you mean?

[dutterbutter]

@GregTheGreek I think we should reference the db in the chain_store

What do you mean?

The RocksDb struct should be accessible in the chain store.

[GregTheGreek]

seperate pr ?

[dutterbutter]

separate pr ?

I will leave it up to you...it would be a small addition though.

[austinabell]

separate pr ?

I will leave it up to you...it would be a small addition though.

Usage of it in this, especially since I am making changes on this in another PR, probably best to leave as is. I can add it in the one where I make changes to this (#132)