Add devman to CMake
Added ctx, first functions

cpu_usage, free ram/swap, uptime
Add function which counts total cpu usage
Add function which returns string with cpuload
Add function for enumerating network devices with MAC addresses
Add function returning RPi serial number
Add function to get information about filesystems
Add function to get RPi CPU temperature
Use devman to get statistics
Merge pull request #3 from maciejaszek/devman

Devman