Factor out deregistration code
Correcting names
Add more functions
Merge.
Merge branch 'dev' into 3p_reg_forward_registers
Brining into line with IfcHandler signature changes
Using trusted port rather than hardcoded 5058
Code complete - deregistering implemented
Some changes noticed in self-review
Applying review markups
Merge branch 'dev' into 3p_reg_forward_registers

Conflicts:
	include/constants.h
	sprout/ifchandler.cpp
Making some minor corrections, including to how the Expires header is generated
Use const refs rather than copying.

Better string passing code.
Merge pull request #15 from Metaswitch/3p_reg_forward_registers

Third-party registration - code and UTs for forwarding REGISTERs on
Fix memory leaks and cope with NULL aor_data.
Merge pull request #19 from Metaswitch/3p_reg_forward_registers

Fix memory leaks and cope with NULL aor_data.