Add "/resources" endpoint

- basic support for /resources endpoint
- configurable cpu / memory allocation to agent (default to system values)

Counting reserved CPUs/Memory is marked as a TODO, since we don't yet have a way to enumerate created containers.

/cc @pb @xla @jmyounker 
`/proc/meminfo` is -- to the best of my knowledge -- the authoritative source of total available memory for a host. It's also pretty-formatted, making `scanf` ideal for parsing out the info.