Refactor parts of the logging/tracing framework.
Refactor the build setup and main entry points.

This commit slightly changes the layout of the build.

    - We now keep all binaries in build/bin and all libraries in build/lib.

    - There now exists a top-level vast.h for those using the library. This
      file provides two framing functions that have to be called before and
      after VAST. These are vast::initialize() and vast::cleanup().
Keep compiler environment in config.status.
Add colors to command line help banner.