CMake

[b-scholz]

There are few TODOs/improvements left that were mentioned by @TomasPuverle in an early version of the CMake port:

• Replace all the shell scripts (e.g. souffle-compile and all the testing helpers) with Python so it's cross-platform. @b-scholz has agreed it's ok to have Python as a dependency

• See if we can call back into cmake so that we have a better mechanism for building consistenly rather than trying to thread compile flags etc into e.g. souffle-compile

• Make it easier to include Souffle as a subproject using add_subdirectory

There is also a problem with the brew formula on MAC OS X due to the absence of the git repo and problems installing bash-completion correctly via brew.