Refactor cache to use CassandraStore. WIP (does not compile)
Make cache transactions compile
Make DiameterTransaction match CacheTransaction
Get cache UTs to compile
Make handler UTs compile
UT fixes
More UT fixes
Move cassandra test utilities to cpp-common
Exclude some test code from coverage, as well as cassandra_store.cpp (which is jointly tested with memento).
Take some cassandra store cpp-common updates
Merge remote-tracking branch 'origin/master' into cache_refactor
Merge remote-tracking branch 'origin/dev' into cache_refactor
Merge pull request #137 from Metaswitch/cache_refactor

[Reviewer: Rob] Refactor the cache to use the new generic cassandra store.