Fixed readonly inputs on Run > Metadata. Fixes #537

[bodom0015]

Problem

When viewing a read-only Tale, some inputs on the Run > Metadata view are still editable. This could cause confusion.

Fixes #537

Approach

• Updated the License/Environment dropdowns to be read-only when the user cannot edit the Tale
• Disable the Generate Illustration button when the user cannot edit the Tale
• Updated the Description input's Markdown Editor to show the Preview tab by default, and to prevent editing in the Edit tab

How to Test

Prerequisites: Register the LIGO Tale (or another read-only public Tale)

1. Checkout and run ths branch locally, rebuild the dashboard
2. Login to the WholeTale Dashboard
3. Navigate to the Run > Metadata view for the LIGO Tale
4. Attempt to edit the License or Environment
   • These dropdowns should be disabled
5. Attempt to edit the Description
   • The Markdown Editor should be defaulted to the Preview tab
   • The textarea in the edit tab should be readonly
   • You should be able to copy this text to your clipboard, if desired
6. Attempt to Generate a new Illustration
   • This button should be disabled