Split the html form wrapper out of the happstack utils

Also extend it a bit more to cope with less trivial JSON.
This is needed for the way aeson encodes Haskell enum types.
Add another templating helper function

For templates using enumeration types in forms
Add more features to the admin account view/edit UI

Password set and reset. Edit extended account info.
Make admin forms a bit clearer visually
Don't use the css box class on the forms

Hangover from the old hackage html/css.
Flesh out the admin interface with a few more features

Finding outstanding account and password reset requests.
Legacy passwords.