Adjust links

[Zack-83]

This Pull Request contains minor improvements to the README documentation.

• Replace the links to chapter numbers with links to the chapter titles (which are more stable)
• Move field obligation to one separate column
• Prettify the "back to table" links
• Adjust a little the code of the tables to improve its legibility

Motivation:

After each new version, the chapter numbers in the best practice guide have changed. I suggest to rephrase the links within the one-pager guide to make them more persistent and to restructure a little the tables.

[dgarijo]

Thanks @Zack-83,
let me have a look before I approve the changes.

[Zack-83]

Some fields are still not documented in the vocabulary checklist https://dgarijo.github.io/Widoco/doc/bestPractices/index-en.html:

• editorial note
• imported ontologies
• introduction
• the four serializations

[dgarijo]

I need to come back to review this again. Apologies for the delay