Roughly works but need more work and polishing. The workspace plugin
is temporarily disable waiting to be fixed.
Now the application does no longer 'chdir' into the project directory
and we removed the concept of project's directory (core.project_dir)
and project's files (core.project_files). Instead we have always a
project that can contain zero, one or many directories or files.
No directory is special within a project, there is no longer a concept
of project's directory.
WIP adapting open-file command to open a directory
Crash when adding a file into the project
ac0dba18de