Interop (freebsd <-> linux measurements)

With this branch I tried to make the controller more OS independent and allow for "mixed" measurements between FreeBSD and Linux daemons using a Linux or FreeBSD controller.

Some minor (cosmetic) issues remain:
- The header "unit" of the kernel columns still depend on the controller. A controller compiled on Linux will always display [#] while a controller compiled on FreeBSD will always display [B]
- Kernel Columns which are not reported on FreeBSD are always displayed as zero (or in case of ca state as "open") it would be nice to omit these or display "na" or something. 

The Summary Line was changed to include the OS name and release, e.g.:

\#   0 S: 192.168.122.75 (FreeBSD 9.1-RELEASE), random seed: 1496002107, sbuf = 32768/0, rbuf = 65536/0 (real/req), SMSS = 1448, flow duration = 10.000s/10.000s (real/req), through = 148.545713/0.000000Mbit/s (out/in), request blocks = 22667/0 (out/in)
\#   0 D: 192.168.122.1 (Linux 3.11.0-rc4aha+), random seed: 1496002107, sbuf = 16384/0, rbuf = 87380/0 (real/req), SMSS = 1448, Path MTU = 1500, Interface MTU = 1500 (Ethernet/PPP), through = 0.000000/148.598835Mbit/s (out/in), request blocks = 0/22667 (out/in), IAT = 0.004/0.441/4.197 (min/avg/max)