First pass of memento docs
Tody up
Use P-Served-User
Update after review
Merge pull request #6 from Metaswitch/memento_docs

[Reviewer: Matt] Memento docs
Update cpp-common to master
Correct test comment
Merge pull request #9 from Metaswitch/p_served_user

[Reviewer: Matt] Use P-Served-User
Set nginx config up for IPv6
Correct iFC
Further corrections to the iFCs
Merge pull request #11 from Metaswitch/ipv6

[Reviewer: Ellie] Set nginx config up for IPv6
Change Metaswitch submodule refs to ClearwaterCore