Some fixes to the documentation about the new sandbox
Small fix

This code isn't needed anymore since 08662f065a88971ff5850c19e596371bb5ad8ed7.
Fix Evaluation creation

Since job.evaluations is a dict that has been decoded from JSON, its
keys are strings and thus need to be converted back to integers.
Add Six dependency
Define a generic and flexible constuctor for Base
Implement a smart MappedCollection
Set reasonable default values for column properties
Remove all specialized constructors from cms.db
Make all code use the new constructor syntax for classes in cms.db

By fixing the order of positional arguments, using keyword arguments
where needed, etc.
Workaround Job's improper use of Testcases
Use the psycopg large object API properly

See http://initd.org/psycopg/docs/usage.html#large-objects