c14n inconsistency

[peter-]

The comment in __init__.py in line 32 states "exclusive" c14n is used by default:

:param default_c14n_alg: The URI of the default c14n algorithm (c14n exclusive by default)

but the actual code in line 42 defaults to "inclusive" c14n:

default_c14n_alg = pyconfig.setting("xmlsec.default_c14n_alg", constants.TRANSFORM_C14N_INCLUSIVE)

Either the docstring or the code should be changed to match the other.
Rainer already quoted the SAML Metadata spec in #27 (specific comment) so the code should be changed to match the comment and the spec.