Configurables did not allow more than one "method" option, and mixed
scenarios (options+methods+...) were sometimes flaky, forcing the user
to know what order was the right one. Now, all options work the same,
sharing the same "order" namespace.
Backward incompatible change: Options are now required by default,
unless a default is provided.
Also adds a few candies for debugging/testing, found in the
bonobo.util.inspect module.
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