Problems resolved:

- Method create_self_signed_cert() was invoked nowhere. This puts parameter "SAML_SIGN_REQUEST" description in configs/development.py as incorrect
- Method create_self_signed_cert() was returning error while trying to write out certificate and private key. File handler was opened for writing out TEXT instead of BINARY data

Enhancements:

- Two new parameters are introduced SAML_CERT_FILE and SAML_KEY_FILE. User can now explicitly define own certificate and key file anywhere on file-system.
- If parameters mentioned in previous bullet aren't explicitly defined, in PowerDNS-Admin root directory self-signed certificate will be created.
- Certificates will be used or generated in any case, because in saml.py there are explicit parameters defined which require certificate/key in order to work normally. If they aren't, exception will be thrown. Examples of parameters defined in saml.py requiring certificate: wantAssertionsEncrypted, signMetadata, wantAssertionsSigned.