A base implementation of
SignatureTrustEngine which evaluates the validity and trustworthiness of XML and raw
signatures.
When processing XML signatures, the supplied KeyInfoCredentialResolver will be used to resolve credential(s)
containing the (advisory) signing key from the KeyInfo element of the Signature, if present. If any of these
credentials do contain the valid signing key, they will be evaluated for trustworthiness against trusted information,
which will be resolved in an implementation-specific manner.
Subclasses are required to implement
#evaluateTrust(Credential,Object) using an implementation-specific
trust model.