Update print/logging

[lcgraham]

Remove print statements and create log files.
Add warning and options (verbosity) for log files. Use a logging module.
Updating warnings when certain algorithmic options occur, e.g., re-normalizing the probability measure because positive probability was assigned to an output event that was not approximated by a contour event. This can be detected at the point of constructing the io_ptr and we may want to generate a log-file containing the output cell(s) (e.g., as identified by point(s) in the output data space defining the cell(s)) that were not approximated either due to insufficient sampling or assigning support of the output density outside of the range of the operator. This is very useful information.

[lcgraham]

https://docs.python.org/2/howto/logging.html#logging-basic-tutorial
https://docs.python.org/2/howto/logging-cookbook.html#logging-cookbook
https://gist.github.com/JohnCEarls/8172807
https://github.com/jrs65/python-mpi-logger/

[lcgraham]

Serial logs work. There probably needs to be additional work done for logging with mpi4py

[smattis]

Maybe only log if comm.rank==0 ?

[lcgraham]

Maybe, but there might be situations where you want to know what each processor is up to since they sometimes do different things. There are a couple of mpi logging implementations using mpi4py that I've linked above, but I don't think adding the mpi logging need to be taken care of immediately.