CMake build system

Introducing CMake to ODTONE.

Thumbs up points when compared to the, at least, current available Boost build system (b2/bjam) configuration:
- full dynamic linkage (bye bye static linkage of libnl & Co.)
- no need to have the full Boost source tree nor compile b2 locally, headers are more than enough to compile ODTONE
- simpler compilation steps IMO (compile flags are set by cmake rather than manually by users)
  * $ mkdir build; cd build; cmake ..; make; sudo make install
- binaries are installed in standard system directories (configuration files in /etc and such)
- dependency detection

To be done/improved:
- refine libodtone splitting in multiple library files instead of all-in-one file (improvement, easy to do)
- generate documentation (missing)
- Windows support is absent using cmake. Use bjam for now. (missing)
- dhcp_usr support (missing, easy to do)

Notes:
- bjam wasn't touched and should not conflict in any way with cmake. Users can continue using it, though they're encouraged to try cmake because it resolved lots of compilation and installation issues reported in the past