use WindowsIdentity.GetCurrent for header

fixes #2031
Correct defaults for suppressing the ambient tx
Letting the ambient transaction control if we enlist or not

If not the send won't enlist in ambient transactions
put get-help about_NServiceBus back

https://github.com/Particular/NServiceBus/commit/8837ab486ba5b23dd73d326d2a54f4351b29273d#commitcomment-8058134
Merge pull request #2494 from Particular/WindowsIdentityGetCurrent

use WindowsIdentity.GetCurrent for header
FinishedMessageProcessing not fired for messages that fail FLR and SLR

Added a failing test proving StartedProcessingMessage is not invoked for messages without an ID
Fixed StartedMessageProcessing behavior
Added a failing test for invoking FinishedMessageProcessing after sending to SLR
Added raising FinishedMessageProcessing when handing msg off to SLR
Patched Distributor in the core
Merge branch 'hotfix-5.0.2' into develop
Fixing merge conflict
cleanup on InMemorySagaPersister
add When_reply_from_a_finder
Merge pull request #2522 from Particular/replyFromFinder

add When_reply_from_a_finder
clean up When_reply_from_a_finder
Made event stream event structs
Updated acceptancetests nuspec to include rx
Merge pull request #2506 from Particular/transaction-defaults-cleanup

Correct defaults for suppressing the ambient tx
add test for cant convert to transport message
Narrowing scope on Message variable
remove exception variable