DB based certificate/key management
<ul>
<li>The formerly file based key/certificate management has been moved to the database. This results in less file IO and more stable operations in cluster mode. R/O and access problems to keystore files are no longer an issue during operations.</li>
<li>Added the possibility to export a full keystore file from the certificate manager</li>
<li>Added the possibility to import a full keystore file to the system at server start</li>
<li>Removed several filesystem based configuration checks regarding keystore files</li>
<li>Removed several keystore file related server settings and configuration interfaces</li>
<li>Importing a private key into the certificate manager did not test for an existing alias - if the alias did already exist the import was just skipped without any error message</li>
<li>If you use Postgres and the database was not reachable there was just a NullPointer Exception - now there should be a proper error message</li>
<li>Dependencies: Updated jetty to 10.0.18 (embedded web server)</li>
</ul>