Reflectometry import - read/write project, show import warnings/errors, item selection, UI improvements

This MR is polishing the import for reflectometry to be ready for release. It contains

• Improve file import regarding content guessing and performance
• Reading & writing of project data related to file import
• Presenting import warnings/errors
• Item presentation/selection on the UI (divided in 1D/2D, include warning states)

On its way there has been a bunch of refactorings as well (renaming, getters/setters, OOD)