Add a simple implementation of a table to present submission results per group #382

[gkreitz]

Implements a results overview table showing results (score, worst runtime, verdict) per group for all submissions. I think the feature makes sense for all problems, not just scoring, so I didn't limit it.

No fancy colors, but I think it's a step up even without colors. We are a bit limited in what we can do here - we absolutely want to send these as messages via the Diagnostics object, and I'm not sure we want to throw color codes down that path.

gkreitz@norn:~/problemtools$ ./bin/verifyproblem.sh examples/oddecho
...
Submission results:
   Submission  sample       subtask1      subtask2      Pts  Time 
   echo.cpp    AC(0):0.00s  AC(50):0.00s  AC(50):0.00s  100  0.00s
   js.py       AC(0):0.05s  AC(50):0.05s  AC(50):0.05s  100  0.05s
   sol.py      WA           AC(50):0.05s  RTE           50   0.06s

Even for problems with one group, I think the table improves readability:

gkreitz@norn:~/problemtools$ ./bin/verifyproblem.sh examples/hello
...
Submission results:
   Submission       secret    Time 
   hello.cc         AC:0.00s  0.00s
   hello.java       AC:0.04s  0.04s
   hello.kt         AC:0.11s  0.11s
   hello.py         AC:0.05s  0.05s
   hello.rs         AC:0.00s  0.00s
   hello_alarm.c    AC:1.00s  1.00s
   hello_alarm2.c   AC:2.00s  2.00s
   readfile         AC:0.05s  0.05s
   hello_alarm.c    AC:2.00s  2.00s
   hello.cc         WA        0.00s
   memory_limit.cc  RTE       0.00s

Fixes #382