Build Script efforts

Created by: cor3ntin

Issue to publicly keep track of an ongoing effort to clean up the cmake build scripts

The goals are numerous

Improve the reliability and maintainability of the build scripts

• Move the cmake files to 3.x and will make heavy use of the target__xxxx commands to limit the number of globally defined variable. It should make the dependency tree more clear and clean.
• Make the files compiler agnostic
• Remove configuration or test specific settings and will put them in CTest files.

Better Packaging and Qt5 support

• Test whether we can use CPack especially with windeployqt and macdeployqt.
• Try to get rid of the aseba-windows and aseba-osx repositories so we would just have aseba and aseba-ci-integration

Better Usability and Tool-ability

• reorganize the build tree so that all built binary end up in the same location,
• Reorganize the source tree to make it easier to comprehend.
• Move the sources to a source subdir
• Move the third parties to a top level dir, hopefully with proper licence. That concern things like avahi-compat-libdns_sd
• Make it possible ( not mandatory ) to manually clone dashel and enki in the aseba source tree to have aseba build them for us, imitating the LLVM model.

Cross compilation

• Investigate whether cross compilation would be suitable to build the projects for windows and mac on docker containers.

And, hopefully, not break anything.