Feature request - have documentation on the main page and a link to the actual tool

[RieksJ]

This is to remember the point made in #27 that called for something useful on localhost:8083 (or whatever other port is configured).

The idea is to have some documentation there (once it is sufficiently stable), that contains a link/button that navigates to http://localhost:8083/ctwg/mrg.

We may want to

• add some texts to the form presented at http://localhost:8083/ctwg/mrg to remind users of what's to be specified where, and
• stretch the field where the user can specify the curatedir, so that you can actually see the whole thing (paths to be filled in here tend to be lengthy).