Update link target to Lucene 5.5 query syntax, moving the link to the page.

Update the link target to the query parser syntax page of the 5.5 version.

Refactor the `LuceneSearchPage` to use an `ExternalLink` for the link
to the lucene page, so that the link target is kept and updated in the
Java code. Move the link out of the language files. This was way too
cumbersome to update the link target (which is probably why no one ever

The query help text is changed to contain a variable:
`gb.queryHelp = here be some ${querySyntax} help`, which is replaced by
Wicket with a link.
The link text is a new lange file property: `gb.querySyntax`.
16 files changed