Documentation: Forrest 0.9 is being removed from ASF Jenkins

[dave2wave]

See https://issues.apache.org/jira/browse/INFRA-27339 where Forrest 0.9 is being removed from ASF build systems.

A search of the codebase shows that a patched version by PJ is preferred.

./src/documentation/publish-poi-site.txt:35:You also need to install Apache Forrest. Forrest is no longer maintained but PJ has a fork with a few small changes.
./src/documentation/publish-poi-site.txt:36:This is at https://github.com/pjfanning/apache-forrest-0.9
./src/documentation/publish-poi-site.txt:38:You can use the last official Apache Forrest release but you may notice some diffs when you build the site and try to
./src/documentation/publish-poi-site.txt:39:publish it. https://forrest.apache.org/
./src/documentation/publish-poi-site.txt:41:You will need to create an environment variable called FORREST_HOME and set it to match the directory location
./src/documentation/publish-poi-site.txt:42:where you installed Apache Forrest.

So the instructions need to be adjusted.

There is a Jenkins file in the repository, but is it current? If so, then this will probably break:

./jenkins/create_jobs.groovy:262:            env('FORREST_HOME', poijob.windows ? 'f:\\jenkins\\tools\\forrest\\latest' : '/home/jenkins/tools/forrest/latest')
./jenkins/create_jobs.groovy:489:            env('FORREST_HOME', xjob.windows ? 'f:\\jenkins\\tools\\forrest\\latest' : '/home/jenkins/tools/forrest/latest')

[pjfanning]

The web site is built manually on people's laptops and the files checked into the asf-site branch (content folder).
If some Jenkins build starts to fail, we will fix it but at the moment, I'm going to assume that those FORREST settings for Jenkins are not used.