Display the correct trash or trashforbidden icon and tooltip in the cylinder table.
This should fit together with if it is really possible to remove a cylinder.
Search for "same gas" based on used cylinders only. Otherwise one could remove
a used cylinder because there is an unused cylinder with same gas.
ToDo:
In planner update trash icon on change of planner points.
Signed-off-by: Stefan Fuchs <sfuchs@gmx.de>