Enabled the assignment of the variable env via config files

This feature is just an extension of an existent feature. Today the only way to send environment variables to SGE via bob.bio.base is setting the optional argument --environment. This MR allows us to set that via configuration files by adding env=MY_VAR=VALUE.

Before any complains, I can't come up with test case for that one. This is injected directly in the Namespace object (argparse) AND this object is not visible when we I call verify.main().