Update docs to match recent changes

[dlareau]

In general the docs have not been updated to match the last two releases and the pending new release
Some specific notes from user @nouyang:

• note for puzzle creation: both link and display require zip or PDF files, not html. only difference is displaying to end user, one is in iframe, the other opens a new tab with just the html.
• to make puzzles appear - change "puzzles solved needed" on puzzle page to 0. Then go to staff page, maangement, release initial puzzles
• make prepuzzle documentation clearer
• "Linking an unzipped Dropbox folder for the resource link will also work"---> this appears to be outdated documentation?