Removed the application states "no project" and "empty project"

Description

Removed the application states "no project" and "empty project". These states are not useful for the user and just require more mouse clicks to create a new project and to add the additional content.

We change the setting that defines what has to happen on startup - it controls if a new project has to be created or the last used project or, to be done later, the welcome screen has to be shown. We introduce a new settings that controls what has to be created initially for a new project (worksheet, etc.)

simplescreenrecorder-2023-12-19_19.43.55

This MR addresses #608 (closed) as well as the problem with very wide default panels for the project and properties explorers when the current project is closed and there are no other docks shown so the default docks take the whole space - with this proposal there is always an object shown initially (which still can be closed, but this will be addressed differently).

Conformity

• Changelog entry
• Unit tests
• Update INSTALL
• Downport~~
• Fixes: #608 (closed)

When external dependencies are removed

• Reporting to ...