Confirm discard dialog

[Licenser]

When editing something and making changes and then pressing X or cancle a dialoge about 'do you want to discard your changes' would be nice.

The concrete case where I ran into it was:

• open a item
• assign a unit
• then close the window

This was not saving the unit even so the unit was listed which lead to some confusion, so having a window about 'discard' would be neat.