Support for running non-node applications

[agallant]

Radiatus would be a more useful platform if it could easily run applications from beyond the node/npm ecosystem. At minimum, this means some sort of sandboxing/containers - Docker is a tempting and popular option, but would need some due diligence.

[agallant]

A little bit of research about what's out there:

• "Sandstorm's server-side sandboxing is based on the same underlying Linux kernel features as LXC and Docker. We use the system calls directly for finer-grained control." It looks like they depend on https://github.com/seccomp/libseccomp so that's one possibility.
• For a more JavaScript-y option, https://github.com/mnylen/pig is a "tool for configuring and starting Docker containers in development and ci environment." Doesn't look like it has support for permissions/API type settings, but it does look like an easy way to fire off a Docker instance from node.

[agallant]

Redundant with #34 and #35 (which let us split out the separate concerns).