The Finish Loading switch controls both loading and unloading

[bjbeare]

TL;DR
Both Finish loading and unloading are useful concepts and need to be separated.

What ?
I suggest separate switches.

Why ?
By being able to finish unloading without having finish loading set, you can ensure that there is no residual cargo when you return to depot.

code
I've coded this and will push my suggested revision. Note.. this is my first foray with .lua so best look at it carefully.