keep class when cloning ttreenodes (even if that class is unknown in the cloning function)
fix cloning for patterns, better visiting for queries and pattern terms
cloning for template elements, visiting for patterns implementation
add closures
fix that closure variables where not accessable in patterns that define a new value for the same variable
refactoring: make default txqterm childless, add new level in hierarchy for terms with children
refactoring: rename txqtermnumber -> txqtermconstant
refactoring: remove txqtermstring
implement named function references