Change config file keys to use - as the separator

This way both the flags and the config values use the same separator,
reducing the potential for confusion.
Cosmetic change in error message
Make Context.Reverse return absolute URLs for host-specific when possible

App.Reverse still returns a protocol relative URL, since it has no
way to find the current request protocol.
Add Context.BasicAuth

Returns Basic authentication info
Accept the form tag "line" as well as "singleline"

We'll eventually remove singleline