Avoid duplication of member variables for location and momentum of the...

Avoid duplication of member variables for location and momentum of the reference particle and the transformation from the reference to lab coordinate system. Deleted the member variables in the ParallelTTracker and just using the ones in the PartBunch. This is a first step towards #287.

The reference tests all ran without additional failures and the bERLinPro also yields the same results.

Minor change I've forgotten to mention: I've removed using namespace std in ParallelTTracker.cpp and added std:: in a few locations. I prefer to add std:: where it's needed instead of adding using namespace std.

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merged

mentioned in commit 82e4991f