Add dynamic loadable library abstraction to stout.

Adding a first class primitive, abstraction and process for dynamic library writing and loading can make it easier to extend inner workings of Mesos. Making it possible to have dynamic loadable resource allocators, isolators, containerizes, authenticators and much more.
I think this could be a powerful feature, as we get even more extensible and flexible ways of setting up Mesos - but also for isolating dependencies and complexity in external libraries and to ease experimentation with new features. For example, imagine a loadable allocators which contains a VM (Lua, Python, ...) which makes it possible to try out new allocator algorithms without forcing those dependencies into the project.

BenH and I chatted about the concrete details and I will follow up with small write-up/proposal.