simple style correction
created a method by refactoring code. The method
handles the grounding of Criterium Variables.
another small refactor. Works
function mapping the variable's name to the
Criterium (represented by Criterium-String) that use them
 small bug correction and changes in documentation
deal with the constant variable error
check for variable names before setting value of Criterium-variables
Merge pull request #31 from AmeBel/r2l

Fix for issue #23