merged latest updates with changes from eile

this is the big merger of new features, cmake, and file relocations of the previous pull request.

Coming up next:
* the readme update to cover the cmake build
* configuration options to chose it_api over sockets or verbs (work in progress)

@eile do you want to review anything before I complete the pull request?
Also the CMake/common modules lack a Findrocksdb module that would ease the build for the rocksdb storage back-end of SKV.  The ZLIB dependency is already covered here. Depending on preference, we could include the ZLIB dependency into the Findrocksdb module and then remove it from here.