Add user friendly errors

[skybird23333]

If you execute logs command without the process argument for example, JanD returns something like this:

JanD v0.6.0
Getting last 15 lines of stdout logs...
Unhandled Exception: System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at Internal.Runtime.CompilerHelpers.ThrowHelpers.ThrowIndexOutOfRangeException() + 0x20
   at JanD.Program.<Main>g__TailLog|6_1(String, Int32, Program.<>c__DisplayClass6_0&, Program.<>c__DisplayClass6_1&) + 0x1a3
   at JanD.Program.<Main>d__6.MoveNext() + 0x1740
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x1c
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task) + 0xc5
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task) + 0x46
   at JanD.Program.<Main>(String[]) + 0x20
   at jand!<BaseAddress>+0x30188a
Aborted (core dumped)

This can be confusing if someone accidentally just forgot to pass the argument, and this error is not exactly helpful in pointing out what happened.