Fix #359 - Introduce build system based on Gulp

Fix #359 - Introduce build system based on Gulp

- Add Gulp and new dependencies to `package.json`
- Add `gulpfile.js` with four tasks:
    - `tsc`: For building TypeScript sources
    - `bundle`: For bundling JavaScript modules in a monolith
    - `sorcery`: For resolving the source map chains back to the original TypeScript files
    - `build` (`default`): Runs the whole `tsc` → `bundle` → `sorcery` chain
- Clean up `Dockerfile`, since `cpio` is not needed any more
- Clean up not needed dependencies from `package.json`
- Remove `bin/build`
- Update `bin/release` to use `npm run build` instead of `./bin/build`