QOL: Error handling and messages

[omeh-a]

Currently, ipbench almost never will let you know what goes wrong. The most painful portion of this is when it fails to compile correctly and the error messages are identical to when it fails to connect to a tester. Eek.

Goal: clear error messages for all common failures. E.g.

Failure to connect
Invalid arguments
Incoherent data returned from testers
Unmarshalling failure
Failure to control remote

Goal: make the few error messages (or help messages) much clearer.

[omeh-a]

More insight: there are actually some error messages contained within, but they are scarcely printed out due to some really bad practice with how exceptions are used in ipbench. I assume this is because most of this exception code was written decades ago.

[omeh-a]

Problem appears to mostly lie within C code - when shunt code fails there is no such thing as exception checking because the SWIG interface is absolutely trivial - things just break.

The best thing to do for now without a large refactor is just to make the crash output on that C code more informative