Added optional base64 and base64url encoding options to fingerprint.

Added a new configuration parameter named `encoding` that allows fingerprint hash values to be created using a more compact base64 encoding in addition to the default hex encoding. Both standard base64 (`base64`) as well as URL and file name safe base64 encoding (`base64url`) are supported.


Should this encoding setting be extended to support our other fingerprint methods? Looks like from the code it only supports hashes coming from the openssl library (sha+md5).