Use an appropriate name in the Reply-To header

Use "Site Name <>" for the Reply-To header when the reply is to the site or a public topic.

Use "username <>" for the Reply-To header only when the reply is to a private message topic.
move website from User to UserProfile
do not use try in UserSerializer for fields coming from UserProfile
Corrected and added appropriate specs to confirm correct behaviour.

Tests ensure that the site name is used for public replies and the username is used for private replies.
Merge pull request #2424 from abezzub/website

Move website from User to UserProfile
FIX: admins should be able to create topics, even if min_trust_to_create_topic is higher than their trust level
Merge pull request #2421 from peternlewis/reply_to_name

Use an appropriate name in the Reply-To header