#1715 Refactor and rewrite in large parts the documentation about CI (especially considering it has changed much since the documentation was first written, with for instance the shared runners now fully functional).

Also overhaul and document better the way to neutralize some CI steps.

- Move some of its content in ancillary READMEs.
- Documentation related to Doxygen has been expanded.
- Move the continuous integration documentation part in the newly created Documentation/Wiki directory.
- Remove Lexicon, which has been moved in the IntroductionTalks project.

Continous integration section still needs to be addressed and updated.

#1713 CMake: add a step to configure properly XCode templates when XCode is used. This modification relies upon a newer functionality of CMake; CMake required version has therefore been updated.

#1566 XCode for Model instances: add arguments to the schemes so that the model may be run directly upon completion of the XCode project creation. One demo file has been chosen somewhat arbitrarily (to my knowledge it is not possible to set an argument in a scheme but leave it unticked).

#1566 Fix the tests that weren't working (mostly due to filenames or symbolinc links that were not updated).

#1566 CMake: add Lua, CMakeLists.txt and README files in target_sources for test so that they appear within the generated IDE.

Also make the naming more consistent: the tests are now mostly called `test.cpp` whereas before it was randomly `test.cpp` or `main.cpp`

#1566 Modify generate_cmake_source_list.py script so that CMakeLists.txt, SourceList.cmake and *.doxygen files are added to the generated IDE for the main library. ModelInstances and Tests should be handled separately (they are not handled automatically by this script.

#1566 Tests: move Boundary condition into FiniteElement folder. Add organization in IDE for the related tests.

#1566 Tests: Same for Core. Also change the test tools in IDE to match what was done for the other targets.

#1566 Tests: organize properly the ThirdParty tests. In the process reorganize two of them in the filesystem.