Adding Subcontainers to cAdvisor client.

Also refactoring and improvements.
Merge pull request #265 from vmarmol/client

Adding Subcontainers to cAdvisor client.
LXC Factory and Handler

This factory and handler can retrieve memory, cpu, diskio, and network information of lxc containers.
The handler can be passed additional container information(e.g. network interface) using a cdesc.json file