Design/Prototype scalability and deployment support

[kuba--]

Investigate/research and design a new way to scale bblfshd without current internal implementation of container management with libcontainer. There are two layers of scalability:

• scale drivers (we can hide pool of certain driver behind some kind of headless service/load balancer)
• scale native drivers (processes inside a driver, so far it's a single thread - stdio communication)

This task should be mainly focused top level scalability and how we gonna deploy bblfshd.

This task is part of the epic: https://github.com/bblfsh/bblfshd/issues/313