Consider refactoring annotation panel as a dock panel content

[glopesdev]

This would allow manipulating the documentation window more flexibly, including as a separate floating window. This also allows the annotation panel to be part of the working editor layout proper, as currently there is no way to retain the annotation panel state for specific workflow projects.

Implementing this will probably require some care as for the first time we would have dock contents which are not workflow editor views. On the other hand, it would be a good first step towards generalizing the editor architecture to allow docking other kinds of content, such as visualizer windows, on the panel.