substitute logging for all prints

[kalenkovich]

Most of the prints that are now in the code are certainly at the debug level and do not need to be printed to console. The errors are easy to miss because of that.

What I need from logging:

• set the level at the command line (BLABPY_LOGGING=50),
• set the level at the package level (blabpy.BLABPY_LOGGING=50),
• an ability to write full log to a file and a subset to console (to STDOUT).