Draft: Refactored the handling of the dock widgets and their states.

Description

We add the standard dock widgets to our initial default and hard-coded positions first. if the user has changed the position of these docks or saved and restored them from the project file, we put the default docks to our initial/default position when a new project is created or a project is opened where the state of the default docks was not saved. So, we always work with the same initial position of the docks and are not able to save the user-defined settings - this will be implemented later.

The behavior can be tested with the two project files docks_state_saved.lml and docks_state_not_saved.lml - without and with the option "Save dock state" activated. In the first project only the state of the content dock widgets is restored and the default docks are positioned at their default places. In the second project also the positions of the default docks is set to the positions that were saved in the project file.

Conformity

• Changelog entry
• Unit tests
• Update INSTALL
• Downport
• Fixes: #897

When external dependencies are removed

• Reporting to ...