Main window: filtering by value for key "Group".

- added a to/from request button (tbi)

Some bugfixes.

Major structural and design changes on GUI, classes, parameters...

See merge request !2

Added world link window.
Completion and implementation of all API parameters (tbd: to be tested).

Feature/with submodule

See merge request !1

Changed some folder, script names, namespace...

Minor GUI changes (layout, Name of element)

Renamed the server scriptables.