Added petscviews for KSP and PC, added BCGS test for KSP

[kshyatt]

Now the test/ksp.jl file shows how to set the solver type. I also added a viewer routine in the test, both to show that it actually does use bijacobi and so you can see some performance info. Added a petscviewer for PC as well, in case someone wants to inspect that.

[kshyatt]

Ok, no one had anything to say and this has been open for more than a week, so I'm gonna merge.

[stevengj]

Thanks @kshyatt.

I wonder if we can implement writemime(io::IO, ::MIME"image/png", x) for PETSc objects via PetscViewerBinaryOpen or similar, so that we can get graphical PETSc output in an IJulia notebook etc.

[kshyatt]

I don't see why not? I can also imagine doing fun and silly things with PetscViewerASCIIOpen and UnicodePlots!

One thing that would be quite cool would be to be able to pipe the PETSc monitors to Gadfly or similar plotting libs, or the interactive stuff @timholy has been working on, so we could see pretty perf graphs in real time.