Fix remaining Lucene/Solr Javadocs issue

Java 8 has a new feature (enabled by default): http://openjdk.java.net/jeps/172

It fails the build on:

• incorrect links (@see, @link,...)
• incorrect HTML entities
• invalid HTML in general

Thanks to our linter written in HTMLTidy and Python, most of the bugs are already solved in our source code, but the Oracle Linter finds some more problems, our linter does not:

• missing escapes <
• invalid entities

Unfortunately the versions of JDK8 released up to today have a bug, making optional closing tags (which are valid HTML4), like </p>, mandatory. This will be fixed in b78.

Currently there is another bug in the Oracle javadocs tool (it fails to copy doc-files folders), but this is under investigation at the moment.

We should clean up our javadocs, so the pass the new JDK8 javadocs tool with build 78+. Maybe we can put our own linter out of service, once we rely on Java 8