[2.0] Confirm on cancel changing blueprint

[Hares]

TL;DR

Add confirmation dialog for blueprints & blueprints variables editors which prevents losing blueprint changes, same as done for the interrupts.

What?

Subj. One-line change.

Why?

1. The same is already done for the train interrupts editor
2. It is easy to accidentally cancel blueprints edits by clicking Esc or even clicking Confirm without hitting Enter first (name will be lost)
3. It is easier to accidentally cancel variables edits by clicking outside the window