Add Python quiet function

[ChristopherHogan]

Closes #874.

[klein-j]

I like the idea of this patch, but I don't think it is going far enough. The amount of lines printed by meep where only reduced by about 20% in my program. The selection is also pretty unintuitive. "Field time usage" is omitted, but "Meep: using complex fields." or "Working in 1D dimensions" is still shown. Those are very particular and fine grained information that I am usually aware of rather than some sort of warnings. I don't see why those would still be displayed in silent mode.

In short I think it would be nice to silence all output (and even better if multiple levels of log details would be configurable).