Add validator support. The validator takes a "tree"-ish structure
describing the configuration model, composed of clauses (repeatable or
not) and properties (mandatory or not, as well as their types).
The validator walk in this structure and check for each clause if it
exists, if it is repeated (and allowed or not), if the mandatory
properties are present and what's their type.
What is not handled by the validator (and probably okay) are
non-described properties and non-described clauses (so it is possible to
add more which is not in the configuration file).
Colin Vidal
c2fe3853ef