Ability to run multiple builders

[metachris]

If there's a way to integrate the HA setup with op-conductor that would be huge (cc/ @noot).

Please jam on the design before implementing.

[gpevnev]

@metachris @noot can you please write a bit more about exact use case you have in mind, so we can design how this can work

[gpevnev]

Things to do after call with @avalonche :
Check out how to use BProxy to with multiple builders in playground (currently supports only one)