Refactor HttpStack interface to remove the concept of handlers
Take latest master branch to fix broken UTs

Merge remote-tracking branch 'origin/master' into sto809
Move threadpool.h to cpp-common
Controller thread pool implementation - header only implementation
Move controller thread pool to its own cpp file
Fix some compiler errors
Refactor diameter stack to match HTTP stack
Refactor SAS logging
Add chronos SAS logging utilities
Fix compiler errors
Simplify SAS logging of HTTP messages that have the body omitted
Move chronos SAS logging utilities to httpstack_utils
Extend mock SAS to allow searching for events
Markups
Merge pull request #135 from Metaswitch/sto809

[Reviewer: Graeme][From: Alex] HttpStack changes for sto809