4 unit tests and added setters in class 'Parameter'

Unit tests for all classes in Transformer\Event that have methods.
Two setters added in Transformer\Template\Parameter
Unit test for Transformer\Template\Parameter
When coding I can recommend the following (clean coding guidelines):

- Put your class members in the order of constants, properties, methods
- then put your visibilities in the order public, protected and private
- lastly: order your methods in order of appearance; this means that if a method uses another method of the same visibility, then the used method should be below the consuming method

This order will increase readability of your code by a significant amount because it is based on how often you look for something. (private methods are only ever read when you work in the class itself, protected in that class and any extending classes, public methods by the current class, extending classes and all other classes; hence public is the first you will be looking for, then protected, then private)