Using NODE_ENV to determine if frontend code should be included in the build.

Fixes issue with zip file handling.

Making use of the newly added `buildRomData()` method.

Making use of the newly added `buildRomData()` method.

This has been moved to emukit.

Uses js-sys to interact with the Javascript VM, to obtain Date() reference.

Makes use of the most recent save state support in EmuKit.
Thumbnail image support.

Using static methods instead of global functions.