Move widget stuff into context-editor plugin

Signed-off-by: Daniel Borchmann <daniel.borchmann@mailbox.tu-dresden.de>
Fix docstring

Signed-off-by: Daniel Borchmann <daniel.borchmann@mailbox.tu-dresden.de>
GUI fixes

Signed-off-by: Daniel Borchmann <daniel.borchmann@mailbox.tu-dresden.de>