REVIEW: NEXUS-5965 - jetty xml cleanup

https://issues.sonatype.org/browse/NEXUS-5965

- generally update for Jetty 8 and simplify config
- remove jetty DefaultHandler as from my debugging it is never called upon or needed anyways
- add InstrumentedSssChannelConnector/doStart support for ssl example
- add InstrumentedHandler around NexusWebappContext to expose metrics
- remove disable taglib hackery and support class
- remove https redirect support class not used and obsolete
- apply sonatype formatting
- fix https redirect examples to use modern security constraint strategy
- rename some example files to better describe purpose ( I think)
- make jmx example work better out of box
- add kitchen-sink example that combines jmx, https enforcement, and access logging all-in-one