#8 add option to clean Entities on parsing

[Anonymous]

Scenario:

I parse a file with 3 concepts. I remove 2 of them and
parse the file again, with the current behaviour one
always ends up with still 3 concepts.

Suggestion:
add a parameter to the configuration map of the parser,
that allows to determine the behavior of the parser
(either clean all definitions from the TopEntity that
is parsed or add them to the known descriptions.