[TASK] Add unittests for t3lib_div::*List functions

Some of the most basic functions should be covered with unit tests.

The change creates tests for inList, expandList, rmFromList
and uniqueList.

Change-Id: I0fd1e47d7aec96e950b69b4c44898e55920ff4fd
Resolves: #36968
Releases: 6.0
Reviewed-on: http://review.typo3.org/11089
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn