Include only documentation tests in the -DdocsBuild.

Makes it possible to run documentation related tests only, speeding up work on documentation a lot.

The tests executed in a -DdocsBuild matches one of:
* named *DocTest,
* named *DocIT,
* named *FunctionalTest and located in community/server,
* located in the docgen package of the Cypher module.
(and a few more variations with no current matches)