Imporoved and shortened conf.py code

Imporoved and shortened conf.py code

Removed subtrees, now only one namespace
Transparent variable creation upon lookup
Implemented general condition clauses (AND, OR, NOT, ==, !=)
Conditions now have 'parent' condition (containing condition block)
Variables refer to only one condition (and indirectly its parents)
Renamed get_value -> evaluate and evaluate -> value
Improved max-depth checking
Updated the test/example (still no conditions)
pprint replaced with dump (for consistency, but still returns an iterator)
Some dovumentation (with TODO's)