Add blocking signal feature

[fcollonval]

Reference

Add blocking signal feature - this inspired by the Qt signal API.

Use cases are:

• To reset an object to a given state
• When you are synchronizing two objects, you need to temporary break the signal loop (this is the primary goal to ease code clarity for synchronizing modelDB and shared models).

It will block signal emission for the duration of a synchronous callback

Code changes

Add

• ISignal.block(callback: () => void): void to block a single signal during a callback execution
• and Signal.blockAll(sender, callback: () => void): void to block all signals during a callback execution from a given sender.

[fcollonval]

Thanks @afshin for the enhancement

[fcollonval]

@meeseeksdev please backport to 1.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 1.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 c90adeee035170719731ccb58c06dfdc1c925460

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #443: Add blocking signal feature'

4. Push to a named branch:

git push YOURFORK 1.x:auto-backport-of-pr-443-on-1.x

5. Create a PR against branch 1.x, I would have named this PR:

"Backport PR #443 on branch 1.x (Add blocking signal feature)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.