This will allow us to notify the parent about changed parameter values.
Accompanying changes and problems:
- The default constructor ParameterPool() is deleted, to enforce
  presence of a parent.
- Therefore several tests had to be outcommented (marked as
  TEMPORARILY DISABLED). Improved tests should make more
  realistic use of ParameterPool, providing it an IParameterized* parent.
- The function IParameterized::getParameters() is outcommented.
  It was only used in some tests, and for printout. In printout
  functions, it is temporarily replaced by fixed text.