PropertyAttributeConvention does not apply to non-public properties

[anfomin]

Both PropertyAttributeConvention <T> and NavigationAttributeConvention<T> does not apply to protected and private properties. They use method Type.GetProperty(name) to get CLR property which always returns null for non-public ones.

[rowanmiller]

@smitpatel we don't map privates by default, but we should respect annotations on them once they are included