Code review comment for lp:~edwin-grubbs/launchpad/bug-436229-distroseries-page-titles

Summary
-------

This branch removes redundancies from the $distro/+addseries and
$distroseries/+edit-packaging page titles and labels.

It also makes the $distrosourcepackage/+index and $sourcepackage/+index
pages use the label attribute.

DistributionSourcePackageView.label was just returning the title attribute
from the model, so I did the same for the SourcePackageView.label, and
I updated the SourcePackage.title to format the string just like
DistributionSourcePackageView.title, since that was what the browser code
was doing effectively. The only small change I made to that was to use
the DistroSeries.displayname instead of the title, which made the
SourcePackage.title cleaner.

Tests
-----

./bin/test -vv -t whatever

Demo and Q/A
------------

* Open http://launchpad.dev/...

* Check that the <title> and <h1> don't have redundancies.
  * https://launchpad.dev/ubuntu/+addseries
  * https://launchpad.dev/ubuntu/warty/+source/mozilla-firefox/+edit-packaging
* Check that the <h1> appears above the breadcrumbs instead of below it.
  * https://launchpad.dev/ubuntu/warty/+source/mozilla-firefox/
* Removed fill-slot="heading" which was doing the exact same thing as using
  the label would.
  * https://launchpad.dev/ubuntu/+source/mozilla-firefox/