[PAXURL-271] Support JDK 7 and 8 for build and test

Use jdk8 profile to add javadoc option -Xdoclint:none.

JDK7 chokes on this option, so we need to hide it in a profile
that gets activated by JDK8.
[PAXEXAM-270] Upgrade to OPS4J Master 3.3.0