Respond with 0 length body to HEAD requests over gateway

The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response.
update costura

fixes #1700
Merge pull request #1695 from chrisbednarski/gatewayHead

Fixes #1683 - Gateway logs ProtocolViolationException error in response to HTTP HEAD requests
added acceptance test to verify behavior of 'HandleCurrentMessageLater'
fixed 'done' criteria on context to match actual behavior
made messages serializable, because adding an attribute makes a type much more serializable
Perfomance tests now reports throughput to TC
Added a test to check memusage and performance of the containers
Merge branch 'develop' into sagapipeline