Add option to studio pro to error check on save

Hi all,

I noticed in bigger projects the modeler can get really slow, mostly because of error checking.

We can fix this by setting the error check delay in the preferences to only error check after 60 seconds, so that at least we have a one minute timeframe to add more changes preventing the errorcheck.

But if we now want to make sure that our MF (or page) is correct we need to wait out the delay or run the application.

I think the optimal solution for this is to be able to trigger the error check on save of a document:

1. We don't have the problem of the modeler immediately slowing down after adding something new
2. On demand error checking, not too early, not too late
3. You will have to save your documents anyway so there is no way the error didn't show before you run your application (unless you used save and continue from the run project dialogue)