tests: py: Add suport for stateful objects in python tests

tests: py: Add suport for stateful objects in python tests

This allows to write pytests using the new stateful objects.

To add an object use the symbol '%', followed by the name, type and
specifications (currently used in quota):

%cnt1 type counter;ok # Adds the counter cnt1 to all tables

%qt1 type quota over 25 mbytes;ok # Adds the quota qt1 to all tables

Signed-off-by: Elise Lennion <elise.lennion@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>