Do not store a state in a delegate

[ussserrr]

In QML, it is preferable not to store any state in the model delegate. Currently, we do that, especially for the list widget. Current motivation is that visual representation of the project contains so many very specific properties (such as "is project has been navigated to after an action") so they look out-of-place in the Python backend side.

On the other hand, the "GUI" module title itself suggesting that this whole package is intended to be "Visual representation"-specific and there is nothing wrong to have such concrete values defined in the Python side of code. This will not only resolve Qt official recommendation but also might improve stability and simplify some parts of the app.