Another Big Update!

Updated the way Student stores his courses and lectures into Pairs...
implementation of the second enrolled method in Environment needs to be
looked at

Updated a lot of the methods in Environment
Environment mostly done

Hasn't been tested yet, but all a_ and e_ methods except
a_enrolled(String student, Vector<Pair<ParamType, Object>> list) have
been filled out.

Gave Session a hell of a lot of getter and setters.