Implements reloading of SSL bundles. Netty and Tomcat react to SSL bundle reload and hot-reload their SSL certificates (existing connections use the old key material, new connections use the new material).
Implemented a FileWatcher based on java.nio to watch for file changes.
Adds new properties to JKS and PEM bundles to control reload. If reload is enabled, the keystore / key files / certificate files are automatically watched and reload the SSL bundle if they change (which in turn will trigger reload of SSL in tomcat / netty).
I had to refactor the PemContent class a bit, because we now need to know at 2 places if the PEM SSL bundle configuration points is a URL or PEM content.
Comment From: mhalbritter
@philwebb did a pass over the code, I force pushed this PR with his changes. Besides the Tomcat upgrade which breaks some tests this is ready to merge.