Add templates for talk submissions

[hodgestar]

For PyConZA, we often end up given speakers similar advice on how to structure their talk or tutorial proposals.

It seems like it would be helpful if a conference could write a short Markup template which serves as the default text that appears in the Markdown boxes when a new talk is created. Perhaps the template text could also vary by talk type. Even just one sentence saying what we'd like to see in each box might cut down on back and forth a lot and help presenters improve the quality of their initial submissions.