FIX: Removed included Exprtk - now it's compiled as ExprtkWrapper and it's not needed to include the whole header-library.

FIX: FindBoost.cmake now sets the variable Boost_LIBRARIES, which contains libraries' names, but it also makes them targets, so the other applications can be linked against them. The variable BOOST_LIBRARIES was removed.

Rewitten compilation to simplify CMake scripts and to be able to compile examples just linked with 4neuro without being forced to link/include other dependencies.