Make delphin commands callable from Python

[goodmami]

Commands like delphin mkprof have features beyond what's available in the underlying library (e.g., delphin.itsdb in this case), but these commands are only easily callable from the command line, not Python. The functions in delphin.main should only interface the command line argument parser to a high-level function that implements the logic. This latter function could then be easily called from Python, as well.

These high-level functions could go in some delphin.commands module, or in their respective existing modules if the coupling is tight enough.