Add new output formats

[A-dead-pixel]

oittuser, as one can guess, is just oitt but with user CPU time instead of instrucion count. The difference from oireal is quite small, but this should allow s2j to be used in place of sioworkers' DetailedUnprotectedExecutor, allowing a significant security upgrade without having to modify problems' time limits at all. The sys CPU time is also stored, as it might be useful in the future (maybe in sth like a human-full output format?).

human provides an oiejq-inspired human-readable output. Resolves https://github.com/sio2project/sio2jail/issues/8.

Sample outputs of the latter: (here the first line is a program's stdout)

853564863

-------------------------
Result: ok
Time used: 0.151s
Memory used: 11MiB

-------------------------
Result: runtime error 5
Time used: 0.001s
Memory used: 0MiB

-------------------------
Result: process exited due to signal 11
Time used: 0s
Memory used: 0MiB

-------------------------
Result: time limit exceeded
Time used: 1.5s
Memory used: 0MiB