Fixed and extended PHPDoc comments and added additional @var comments

reset the data directory before each test class is run

moved URI setup to execute()

simplified using the TestRequest class

You now can call get() or post() on it and give it all the wanted
input variables

make sure all globals are available in test requests

fixed tests

The test suite was missing a global keyword to access the $INPUT class.

use original conf directory and only shadow special files

https://github.com/splitbrain/dokuwiki/pull/96#issuecomment-5195756

moved _testing to _test