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
NetworkInterface now contains both VethHost and VethChild
Updated import and comments
Added network stats to raw handler

Raw handler now parses an optional json file with the network interface information, and emits network stats.
Fixed formatting
Renamed container description types
matches with the full path of the container
some more renames
Spec consistency
minor fixes and gofmt
Merge pull request #270 from ashahab-altiscale/raw-network-handler

Raw cgroup handler network support using external hints file