Authors revamp

[abelsiqueira]

Description

While working on #118 and #356, I realised that there are a few things entangled. This will help me organise the work.

• [x] #426
  • Default to the AuthorEmail. Can't be empty.
• [x] #427
  • Default to the AuthorName. Can't be empty.
• [x] #428
• [x] #118
  • Deprecate AuthorName and AuthorEmail in favour of Authors, a comma-separated list of names.
  • Change CodeOfConductContact default to the first email in Authors (regex-willing)
  • Change LicenseHolders default to the list of Authors names (regex-willing)
• [x] #356
  • Implementing multiple authors will enable optional e-mail as well.
• [x] #439
  • Create the issue and the milestone.