issue #1737 NullReferenceException MessageMapper

GenericTypeDefintions can't be mapped except we use constraints
Master branch (4.2.0) doesn't build from source

PowerShell.Tests project fails to build
Merge pull request #1772 from chrisbednarski/FailedMasterBuild

Fixed System.Management.Automation reference
Added support for both Windows 8.1 and Windows Server 2012 R2.
Need to dispose
Should always clear current transaction.
Removing the nhibernate projects since we've moved them to a new repo:
https://github.com/Particular/NServiceBus.NHibernate
References not required anymore
Removed NHibernate nuget declaration
remove some dodgy casting
Making sure that we invoke saga finders in relevance order
Using the new pipeline to get rid of the SagaContext
Deleting the saga context
Removing the obsolete saga finder
Obsoleting the IHandleReplyingToNullOriginator
Auto correlation with sagas in now done in a behavior, 2 less thread statics!
Adding a few types that got removed prematurely
More obsoleted a few fixes based on code reviews by john and simon
Merge pull request #1768 from mbabi/develop

issue #1737 NullReferenceException MessageMapper
update obsolete