new scoping rules

Simplified the scoping rules for Object definitions and static counter variables (eg @Aton:C, @bond:CH, @Angle:HCH, ...). Hopefully this should make it easier to create LT files using namespaces and (nested) class definitions which behave in a way which is more similar to languages like python.

(This may eventually ease the transition to creating a version of moltemplate where static node definitions are implemented as python class definitions. It would be nice to have a version of moltemplate which can be run from within python itself.)