convert artifact string to artifact
When a key name is specified, select the certificate it belongs to.
Use a proc to determine the current time in the factories
Merge pull request #23 from JanDintel/fix-factories

Use a proc to determine the current time in the factories
Added the key_name method to the Signature class.
Moved the key descriptor lookup into the SSO Descriptor Type complex type.
An EncryptedAttribute should only have EncryptedKeys retrieved from the root and not contain EncryptedKey elements obtained through the EncryptedData element.
Merge pull request #21 from digidentity/filter-certificate-by-keyname

When a key name is specified, select the certificate it belongs to.
Merge pull request #24 from digidentity/encrypted-attribute-update

An EncryptedAttribute should only have EncryptedKeys retrieved from the root and not contain EncryptedKey elements obtained through the EncryptedData element.
added a current provider option
added null provider
added controller helper
added xmlenc dependency
refactored saml config
updated readme
minor refactor
merged with master