docs: clean up readthedocs URLs

It will redirect to the canonical URL https://*.readthedocs.io/en/latest , and
there is no point in linking to /en/latest .

docs: smtp_port is now respected by backlash

Support for a custom smtp_port was recently added to backlash, so bump
backlash and update the documentation to reflect that.

docs: update email documentation for TurboGears2

Small update to the documentation.

docs: tweak email documentation - add gmail example

smtp_auth is too obscure to have in the .ini template.

email: send comment and pullrequest mails with the author's name in 'From'

When emails are sent for comments and pullrequest invitations, set the From
header to:
Author's Name (no-reply) <generic email address>

Using the name of the person that causes the email, makes the emails more
useful and interpretable for the recipient of the emails.
To avoid replies directly to the author, triggering an 'offline' email
discussion that is not visible in the Kallithea interface, a generic
'no-reply' email address is used instead of the author's email
address.
This approach is assumed to be accepted by spam filters, as several other
web services are using the same approach.

The sender used for other email types, e.g. password reset mails, is
untouched and remains the value configured in app_email_from.

The sender used for the SMTP envelope is untouched as well.

Based on code by Cedric De Herdt.

docs: consistent spacing around headings

Start out with 2 empty lines before/after for top level, decrease for deeper
levels.

docs: update menu navigation notation to use *Menu > Menu Item*

Follow Apple's notation for 'Menus' from
http://help.apple.com/asg/mac/2013/#apsg1f285825 .

docs: cleanup of casing, markup and spacing of headings

Mostly stuff found and fixed by Søren, extracted here to separate things.

Other uses of title casing might be debatable, but here it was just a few
documentation headings that clearly were inconsistent with the majority.

spelling: use "email" consistently

The common English spelling is "email", not "e-mail" (and was indeed
also the most common, but not only, variant in the Kallithea UI).

http://grammarist.com/style/e-mail-email/