Console expressions should be evaluated in a non-global context

[outoftime]

E.g. declaring a var using the console should not make that variable available to project code. The console should have its own local context for variables.

I believe this can be achieved by having each console expression in the preview frame evaluated locally by a function which then returns a new function to evaluate the next expression.

This should also make const and let declarations work properly in browsers that support them, which they currently don’t.