Description and note fields as markdown strings

[uatisdeproblem]

• Improve the note/description fields of all the entities (organizations, speakers, etc.) to support markdown markup.
• In the pages that allow editing those fields:
  • Turn the inputs into text areas.
  • Add a basic/simple toolbar (or lib?) to suggest the use of markdown language.
• In the pages that view those fields:
  • Convert markdown strings in HTML.