Add automatic parallelization of maps and nested forms

[adamhaney]

Currently python is plagued by the GIL, wouldn't it be nice if we broadcast s-expressions to eager mapping interpreters so that they could be evaluated outside the GIL?

Proposed approach:

• A master process is the command and control that serves as the entry point to the running program
• Workers are spawned in the background on startup and work is fed to them when functions that are guaranteed parallelizable can be called on multiple workers send those functions down to the workers
• Add options to call maps etc without parallelization

[adamhaney]

@joshmarlow and I have discussed this idea further and currently there are two pieces needed in order to implement multiple worker processes:

1. A scheduler which can decide where work should be sent
2. A worker object that can run locally, remotely or in a public cloud