Spec synchronisation. Fixes #3385 Partial changelog: - Add tests - Improve robustness of some tests - Make transmissions an independent package - Begin to work on commands (WIP) - Clean API of some presenters (such as lists) - Work on context menu of Text presenter and table presenter - Drop box list items can now be sorted - Proceed the decomposition of Text and Code presenters - Replace some variables and value holder by observable slots - Improve demos - Table columns are now expendables - ...