As the new versions of JSPWiki contain an installer I want to
override, I need to add a new configuration parameter, which is
currently like this:

--------------------------------------------
Template: jspwiki/baseurl
Type: string
Default: http://localhost:8180/JSPWiki/
_Description: Default application name:
 Please enter the HTTP prefix of the wiki. This rewrites all JSPWiki
 internal link references, so it needs to be correct. It also needs
 to contain the trailing slash.
--------------------------------------------

Corresponding JSPWiki parameter documentation is:

#  BaseURL can be used to rewrite all of JSPWiki's internal references.
#  Sometimes, especially if you're behind a address-rewriting firewall,
#  relative URLs don't work since the servlet container has no idea
#  where it's actually located.
#
#  Leave undefined if you want to rely on what your servlet container
#  thinks of where your application lives.
#
#  You MUST define this one if you want to enable RSS (see below).  In
#  general, this is a good idea to define it anyway.  Do not forget the
#  trailing slash.
#
#  Example:
#  jspwiki.baseURL = http://www.ecyrd.com/JSPWiki/

Responderlle a