FreeBSD free memory stats and don't make too much noise when no procfs is there (or is not mounted on FreeBSD).

Also removed all the ***Friendly stats, which shouldn't be in stats either way (seems more sane to calculate in UI, if needed).

Haven't found any FreeBSD-native way to get I/O stats for ES process, that can be still achieved if you mount procfs, which is supported in FreeBSD.