Update docs to reflect AKA auth
Merge pull request #139 from Metaswitch/av_docs

[Reviewer: Graeme] Update docs to reflect AKA auth
cpp-common update
Merge pull request #141 from Metaswitch/cpp_update

[No reviewer] cpp-common update
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Merge pull request #142 from Metaswitch/cpp-common-overload

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Update homestead_api.md

Fix public_id option
Change Metaswitch submodule refs to ClearwaterCore