Added (failing) tests for TChain
Passing a few of the first tests with a TChain

All but one line contributed by Axel Naumann
Added function to get fEnv variable to check for validity
Working reading of most TChain tests (undeterministic behaviour)
Fix for undeterministic behaviour caused by tree pointer

Contributed by Axel Naumann
Code cleanup in tests
Removed unnecessary Error messages and calls to Setup
Added comment for getter
Avoid reading file on initialize