Add timing and printing utilities

[bdlucas1]

@rocky here are a couple of utilities that I've found useful while debugging, and it would be handy to have them in core. And others might find them useful too. What do you think?

[rocky]

I think I had noticed at least the timing stuff looking at demo from before.

TLDR; Sure, put in a PR and let's see what mmatera has to say. I'd try it out before commiting.

mmatera has timing code that he has been using and there is a whole other project that was started around benchmarking.

But that said, I suppose each thing has its own advantages and disadvantanges, and I'm fine with adding more. It I think its a given that many developers would rather write their own tool that try to see what else is around and use or adapt that. So be it.

As for the expression printing stuff, again, what I works well for me in the debuggers. For showing Expressions and
https://github.com/Mathics3/Mathics3-Module-trepan/blob/master/README.rst#improved-traceevaluation and for printing expressions inside a debugger:

I realize maybe this kind of use isn't the same and perhaps there's other stuff too, and this might be too heavy-weight.

Just explaining that it's probalby not somthing I'll use in this form.

But that said, if it helps you it might help others (including myself after trying it out.)