Header only package or no deps in compiled lib

This PR is a long term one.. Please to not close it (nor merge it) until everything is fine.
I did a PR just to keep you in touch.

DEPS

- [ ] Check CAIRO

DGTAL

- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/arithmetic/SternBrocot.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/arithmetic/LightSternBrocot.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/arithmetic/LighterSternBrocot.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/kernel/NumberTraits.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/base/Bits.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/base/OrderedAlphabet.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/base/Common.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/io/Color.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtal.dir/DGtal/math/AngleLinearMinimizer.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/Board.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/Path.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/PSFonts.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/Rect.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/ShapeList.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/Shapes.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/Tools.cpp.o
- [x] Building CXX object src/CMakeFiles/DGtal.dir/Board/Transforms.cpp.o

DGTALIO:

- [ ] Built target DGtal
- [ ] Building CXX object src/CMakeFiles/DGtalIO.dir/DGtal/io/boards/Board2D.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtalIO.dir/DGtal/io/boards/Board3DTo2D.cpp.o
- [ ] Building CXX object src/CMakeFiles/DGtalIO.dir/DGtal/io/viewers/Viewer3D.cpp.o