Fix workflow editor

[fbacall]

Summary of changes

• Removes the jscolor lib that was violating the Content-Security-Policy and breaking the JavaScript.
• Use the browser's native color input element instead.

Motivation and context

Workflow editor would do nothing when you tried to add/edit nodes.

Screenshots

Checklist

• I have read and followed the CONTRIBUTING guide.
• I confirm that I have the authority necessary to make this contribution on behalf of its copyright owner and agree
  to license it to the TeSS codebase under the
  BSD license.