fixed buged with HTML5 duplication
HTML ignores hash component of URL
no bcc if None
- support more EMAIL_HOST_* params, so that we have more flexibilility using various outgoing email servers
- send all invite emails reusing one connection.
fix broken links when NB is embedded in HTML doc
use absolute links no matter what
Cookie now set by default on root path

This fixes the issue with users having to sign in for each HTML document separately.