Modern and social installation process

[aytekinar]

Restructure the repository tree to have a social cmake support for super projects (cf. Effective CMake and Git, CMake, Conan).

Pay attention to

• decouple src from tests and docs for easy integration in IDEs,
• create a Dockerfile with dependencies preinstalled, and publish it in Docker Hub for fast builds and ease-of-use,
• reconsider the dependency on cURL --- do we really need it for the first version,
• consider a possible integration with PCG (blocked by Convert Makefiles to cmake imneme/pcg-cpp#44),
• make use of conan to support prebuilt binaries of 0MQ, curl, blas, lapack and cereal.

[aytekinar]

Closed. cURL dependency handled, pcg can now be supported via a new template parameter in samplers and encoders. conan is not needed, for now.