Make class BayesDB inherit from object, per modern convention.
Split page for model access and data/metadata access.
Implement bayesdb_cell_value and use it.

Fixes reference to missing bayesdb_cell_code.
Mark unused variables with underscores.
Avoid `file' as a local variable name.
Use iterator comprehensions, not intermediate lists, where fit.
Disable pylint warning about star-args.

The only use of star-args here is where it is necessary.  If it
weren't, it wouldn't be used.