Doxygen comments are now used in libowlps, libowlps-client and
libowlps-resultreader. doc/Doxyfile was added as well as CMake rules to
generate man pages for the libraries' header files.
To be consistent with the other modules, the positioning server must be
called OwlPS Positioner instead of Positioning, and the executable
owlps-positionerd (even if the daemon mode is not implemented yet).
That's a big commit for a tiny change.