[Feature request] New docking system for plugins

[spectralcode]

Is your feature request related to a problem? Please describe.
I'm always frustrated when starting an extension that requires a large GUI and uses SEPARATE_WINDOW as displayStyle. A very large GUI will block the view on to the main applaication and everything else because the extension window is always on top of everything.
Another relateted thing: I think for some OCT systems it may be annoying that the acquisition system plugin is displayed as QDialog (for example if you have settings like scanner offset which you would like to change during an OCT acquisition). It should be possible to dock acquisistion systems and extensions; this would highly increase usability.

Describe the solution you'd like
OCTproZ should use Advanced Docking System for Qt for all plugins (extensions as well as acquisition systems) and for all output windows such as the live B-scan window.

Describe alternatives you've considered
An alternative could be to use the regular QDockWidget system for everything. But this causes trouble on Ubuntu 16.04, because dock widgets cannot be moved properly. On Windows everything works fine.