Reviewer Ellie: Sto536 handlers

Hi Ellie,

This pull request contains the changes that Rob made too, which you've already reviewed. Our changes are independent though, and the files I've changed are as follows:

.gitmodules
Makefile
include/cx.h
include/handlers.h
include/sasevent.h
include/sproutconnection.h
mk/sas-client.mk
src/Makefile
src/cx.cpp
src/handlers.cpp
src/main.cpp
src/sproutconnection.cpp
src/ut/cx_text.cpp
src/ut/mockcache.hpp

The handlers UTs are incomplete and not part of this pull request. There is also a small cpp-common commit to review, which I'll send to you in a second.

There is also a problem with the current code whereby we're deleting the underlying freeDiameter RTR message structure before trying to build the RTA off the RTR, which doesn't work. I'm fixing this at the moment.

Thanks,
Graeme