missing Boost_libraries in CMakeList.txt

[zarquon42b]

linking against statismo_core is not enough because it is only linked against boost_system, the itk module, however uses boost_filesystem.

$ ldd /usr/local/lib/libstatismo_core.so
    linux-vdso.so.1 =>  (0x00007ffe0b1ef000)
    libhdf5_cpp.so.7 => /usr/lib/x86_64-linux-gnu/libhdf5_cpp.so.7 (0x00007f8305ea4000)
    libboost_system.so.1.54.0 => /usr/lib/x86_64-linux-gnu/libboost_system.so.1.54.0 (0x00007f8305ca0000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f830599c000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f8305786000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f83053c1000)
    libhdf5.so.7 => /usr/lib/x86_64-linux-gnu/libhdf5.so.7 (0x00007f8304f25000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8304c1f000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f8306317000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f8304a01000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f83047e8000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f83045e4000)