Minor build system rework

This reworks build system a bit
- Mainly moves CMakeLists parts around to form distinguishable sections.
- Add libinotify support on systems where inotify isn't embedded in the standard library
- Turns Log4Cpp macro in more common .cmake-file
- Simplifies some bits, like using ${SYSTEM_LIBRARIES}

Tested on FreeBSD, but still to be tested on Windows and Linux.