Wss sign custom token

Please consider this pull request so SoapUI can support the SAML Token Profile specification. My company implements the SAML Holder-of-Key security standard (using a WS-Trust compliant SecurityTokenService). Unfortunately it isn't supported by SoapUI yet. 

There are two reasons why SoapUI does not support this now:
1) The SAML (XML) component strips whitespace and breaks the signature embedded in the SAML assertion returned by the STS.
2) To reference the SAML assertion in the Signature KeyInfo, a wss4j custom token key identifier is needed to add the SAML Assertion Id. The SignatureEntry class does not support custom tokens.

```
<ds:KeyInfo Id="KI-5FD1DCF96B933F0CA1139222089937013">
	<wsse:SecurityTokenReference wsse11:TokenType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV1.1" wsu:Id="STR-5FD1DCF96B933F0CA1139222089937014" xmlns:wsse11="http://docs.oasis-open.org/wss/oasis-wss-wssecurity-secext-1.1.xsd">
			<wsse:KeyIdentifier ValueType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.0#SAMLAssertionID">ID_c27deac8-568c-4ee6-a201-6a41bc3cb2a7</wsse:KeyIdentifier>
	</wsse:SecurityTokenReference>
</ds:KeyInfo>
```

This pull request builds further open the previously submitted security patches (SOAP-4586 & SOAP-4430).

http://docs.oasis-open.org/wss/v1.1/wss-v1.1-spec-errata-os-SAMLTokenProfile.pdf