Partially reinstating boost

 * Pylada still needs the header-only libraries of boost at its core (e.g. math/fuzzy.h uses enable_if)
 * The ewald modules needs an erf function from boost.math

So I partially reinstated and cleaned up boost in the cmake file.
The main issue with boost is compiling mpi and python,  which we don't need anymore.

Cleaned up the SNF functions a bit as well.