Add verbose names to URL fields

This makes "URL" show up capitalized in the default template.
Add <thead> and <tbody> to feed list
Add "yarr_confirm" class to generic template

Also move CSRF form element for validation purposes.
Remove "in minutes" qualifier from frequency help

The choices provided already include units, and some of them ("24
hours", the default) conflict with "in minutes".
Merge pull request #26 from twm/feed-management

Minor feed management tweaks