Replaces Expression.Default with Expression.Constant in Processor.
Got a little too fancy - replacing runtime expression compile for getting default value with simple Activator.CreateInstance() call.
New TestNullableInit test to check that Expression.Default is being replaced and not causing exceptions from EF. Also simplified Processor.Default() to remove bool check.
Merge pull request #33 from somedave/master

Replaces Expression.Default with Expression.Constant in Processor.