Adjust error messages that refer to a country

We add the definite article 'the' to the country names that start
'United' so that error messages read better.

Fixes #920
Docs: Updates for dynamically loaded applications

The customisation section required some changes as it's not often
necessary to override the root application instance to change URLs or
views of subapps.
Display non field errors in dashboard for stock records

On this form errors are raised globally and not by individual field.
This commit adds a errors line in the form table. It needs to be added
extra styling to this form.

Fixes #955
Fixes #918
Add "dashboard/base.html" which extends "base.html"

This adds more flexibiltiy to override the default base.html while 
keeping the oscar base.html for the dashboard.

This  can be done by overriding "dashboard/base.html" and then extend
"oscar/base.html" instead of "base.html"
Add additional template block for stock record section

Affects the dashboard product update template.

Fixes #966
Merge pull request #965 from LUKKIEN/feature/dashboard-template

Add "dashboard/base.html" which extends "base.html"
Support icons and namespaced URLs in dashboard nav again

Fixes #967
Travis: Fix migrations and ensure failing

* Use correct username for MySQL on Travis
  Travis docs say username should be 'travis', not 'root'.

* Fail test_migrations.sh if any command fails
  Previously, a failing (non-zero exit code) command would not lead to
  a non-zero exit code of test_migrations.sh. That meant that failing
  migrations would not fail the Travis job as intended.
Bump rosetta version to support Django 1.5
Correct consume_items call for sandbox offer
Ensure basket lines have a strategy instance in formset

This change ensures that each basket line instance has a strategy set
for the BasketLineFormSet.  This means you can access the price and
availability properties of the line.

Fixes #961