Refactor clean task to remove Gulp

[domoscargin]

What

Update tasks/gulp/clean.js to replace Gulp with our own clean script. This task is responsible for watching cleaning a destination directory.

Why

We have made the decision to move away from Gulp and write our own build scripts.

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• [ ] tasks/gulp/clean.js no longer depends on Gulp
• [ ] del package is as up to date as is feasible
• [ ] clean.js has been relocated to tasks folder