Adds 2D video recording option to the GUI.

The GUI now has a snapshot feature. The record button opens a popup
window, which contains the different recording options.

The cog icon now opens a scrollable list of all of the registered
configurations, both local and remote. This window is created
dynamically each time the cog icon is clicked, so it now includes all of the
configurations that were available as the window was created.

The record button now works as previously. To support this change, a
tagging system based on the one from feature/guienhance has been added.
NetConfigurables are now created as peers connect and removed as they
disconnect, which required changes to ConfigWindow.

Iiro Rastas authored 5 years ago and Nicolas Pope committed 5 years ago

A new class NetConfigurable is created, which enables handling of both
local and remote configurations in a polymorphic way.

In the GUI, configurations can now be changed via the cog icon.