[#7109] use user.url() instead of constructing /u/username manually; add sender's name

Using 'user' variable instead of 'username' also allows for more flexibility with
anyone that overrides this template for customizations.
[#7106] cache all jinja templates by default, not just 50 (prior default).  configurable.
[#6893] ticket:507 added current assigned user to input list
[#6893] ticket:507 Rename variable to something more generic