NEW: Added message.h with message macros MSG_INFO and MSG_DEBUG intended to unify and simplify library output.

ENH: Removed relative paths to 4neuro.h, as it's not needed, when the code is given the proper include directory during compilation.

FIX: Fixed relative paths to headers, so it isn't neccessary anymore to include SRC_DIR when compiling examples / independent apps, which only use lib4neuro.

ENH: Added -fPIC option to the linux_gcc_build_x64_debug.sh, so the Boost libraries will be always compiled as a position independent code, even if they're static. It makes possible to link them to the shared library lib4neuro.

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.

FIX: 'ubuntu_boost_system' was incorrectly compiling a local copy of boost which made this continuous integration test pointless

FIX: 'ubuntu_boost_system' was incorrectly compiling a local copy of boost which made this continuous integration test pointless