Add option "Start print automatically after transfer?" or "Only transfer model"

[loociano]

Observed behaviour

In my experience, the printer tends to cool down when printing models that take 3+ minutes to transfer over the network.
When transfer completes, the chart shows a drop in temperature and the printer needs to catch up to its target.

Proposal

Some users may want to control when the print starts. That is, tranfer the model, set the target temperature for some time and only then start the print.

[loociano]

Having this option might alleviate symptoms described in issue #15.