Improved debugging output

Use ToString of the expression as message, this allows usage of
PartialEvaluationExceptionExpression ToString output
Test and fix for NH-3141
NH-3141 - add tests to ensure consistent behaviour with id changes
Rename Contributor Guide.md to CONTRIBUTION.md

So GitHub can recognize it and display on "new pull" request page
Merge pull request #208 from janv8000/master

Improved debugging
NH3392 - Unit test and fix
Merge pull request #239 from gliljas/NH-3392

NH3392 - Unit test and fix
NH3392/Fixture.cs: Minor corrections.
NH-3072: OneToManyPersister improvements
Fix NH-3221
NH-3221 - Correct test case to reference HashSet instead of HashedSet
NH-2756 - Add test fixture
Add support for Convert.ToInt32 / int.Parse

Also support for decimal and double.

NH-2865 : Test case added
NH-3377 : Test case added
NH-2692 - The identity for values or components is the elements themselves,
so return "elements" as property name
NH-2692 - Add KnownBug attribute
NH-3524 - Add support for DateTimeOffset properties in QueryOver
NH-3041 - Add IOneToOneMapper.PropertyReference method
Merge pull request #150 from hazzik/NH-3041

Fix for NH-3041
NH-3269 - Do not map base class properties by inherited class mapping
NH-3135 - Do not map base class collections by inherited class mapping