Add a QML hot reloader to speed-up prototyping

Modifying QML files is a pain: it requires to restart entirely the application and doing several click-actions for each and every small change.

We should invest time to implement a QML hot reloader, it will save at lot of time for developers.

The reloader should reload the QML without quitting the window: I would like to have the app on one side and the editor on the other side, being able to change value on the editor and seeing in almost real-time the changes on the app side.

The QML hot reloader will be part of the application and can be enabled via the QML_HOT_RELOAD=1 envar. and only if the app is bot frozen.