Extract logic from oscar_fork_statics command

Use a separate function that can be tested.
Ensure parent folder is created by oscar_fork_app command

This makes things slightly easier to get started.
Use a base management command class

This makes logging easier to handle. We default to allowing the normal
LOGGING config to specify the logger based on the __name__ property of
the management command module. But if no handlers are assigned, then we
add a STDOUT stream handler.
Use default logger for scores command in sandbox
Improve customer alerts handling

This change refactors the form and view for alert creation.
Use idiomatic map for lower-casing strings
Extract man. cmd. logging behaviour into base class

A bit of a sprawling commit this one. The main change is to extract the
boilerplate logging code into the `OscarBaseCommand` class. This
instantiates the appropriate logger instance and logs the start and
finish of a command.

The alerts module also is extended to allow a logger to be passed to
each function. Some extra logging calls are included too.
Remove oscar.alerts named logger from sandbox
Update reference docs on management commands