* scep: documented the package
* scep/api: removed some top level constants
* scep: removed dependency to pkg/errors
* scep/api: documented the package
Only when a SCEP provisioner is enabled, the SCEP endpoints
will now be available.
The SCEP endpoints will be served on an "insecure" server,
without TLS, only when an additional "insecureAddress" and a
SCEP provisioner are configured for the CA.