The gulp dev task deletes all the built files when they change

[JedWatson]

The gulp task for development isn't set up correctly, it deletes all the built files when one of the watch tasks run.

This is due to limitations with orchestra that will be solved in Gulp 4, but for now is a real pain. The whole gulp file needs to be reworked to fix this, or the clean tasks need to be removed (which I would prefer not to do)...

One possible solution is to create duplicate tasks with dist and dev versions, where the dist versions all depend on the clean task, and the dev ones don't.