Conan TODOs

[Phibedy]

The work-flow sucks:

• it is easy to install but will take forever to build if we pass --build (we would build sdl, opencv etc)
  • we have to get a list of all modules/libraries and pass --build=modules,libraries
  • build them using travis (recommended), conan will update the binaries automatically (it checks the remote binaries)
  • remove all libraries/modules binaries and call conan install --build=missing
• If a library is compiled using -DUSE_CEREAL and another uses it without -DUSE_CEREAL the headers differ. But library will compile, not sure if the binary compatibility is given in that case. If not we should remove -DUSE_CEREAL from the header or use cereal by default.
• port all modules/libraries (not that worse, but flags like -DUSE_CEREAL are painful.