Add option to Save on Build

[matgis-king]

It is possible to lose work if you use an external Git client to pull changes. Any files that changed will be reloaded when you go back to the editor, losing unsaved changes in the process.

If we provide an option to save on build, people can enable it to reduce the risk of this happening.

[paulhargreaves]

Different problem but related. Just had the editor crash and didn't realise there was no autosave/save on build. Lost about an hour, which is no big deal.

Searched the forum and 'editor2' was supported to have this ages ago?