Improve MuranoPL propert/argument contracts

Number of relatively simple improvements can be make to contracts system that would solve most of contract problems.

First part is discussed here: http://osdir.com/ml/openstack-dev/2014-05/msg01752.html

Second part - need to bypass the 'default' in parallel to bypass the main structure, and not to take it as the one piece.

Third part - need to remember "the current route" when traversing and display it on an error.
Accordingly it is necessary to contracts code validation to transfer the name of the audited Property,
 to be able to print in exception for a single Property where the contract was broken