fix variable name conflict bug in pimdec::zeroRad. 

fix variable name conflict bug in pimdec::zeroRad. 
Test with 
Tst/Short/bug_name_conflict_in_zeroRad.tst

Introduces a new method getNewVariableName() in ringutils.lib to get a conflict-free variable name.
For making this possible, 
a couple of new documented and teste procedures were introduced:

Listutils::extendList
Stringutils::splitString
Stringutils::assembleStringArray
Ringutils::getNewVariableName
Ringutils::getNewRingVariableName


Jakob