* Make distinction between DisplayName and Username in email templates
Store the actual username in the variable named Username and store the
separate DisplayName in another variable. This allows us to access the
actual username when we need, which currently fails if a user has set a
full name.
Fixes #6161
* Use u.Name directly
No need for extra function, also change use in all mail sending
functions here
* Don't include Username when not used
This solves the problem of administrators creating accounts for users
that then do not know their initial password (without the administrator
sending it to them via some other channel).
This commit improves templates readability, since all of them use consistent
indent with all template command blocks indented too.
1. Indents both HTML containers such as <div>, <p> and Go HTML template blocks
such as {{if}} {{with}}
2. Cleans all trailing white-space
3. Adds trailing last line-break to each file
