Use order currency for formatting in dashboard

Plus remove superfluous currency_filters from lots of dashboard
templates.
Move RegisterUserMixin to customer.mixins
Fix context data bug in ProfileView

The empty return statement was hiding PageTitleMixin's output
Docs: Add docs for wishlists app
Add tests for wishlists
Fix dropdown menu

This was just the wrong HTML code used for a Bootstrap button dropdown.
Note that this does not fix the issue of scrollbars appearing when the
dropdown is actually clicked.
Use correct get_user_model

That bug was introduced in 869944d6 and caused tests to fail with Django
1.4.
Docs: Discourage admin more

We currently mention it in internals/sandbox.rst. I've added a note to
the dashboard app (ref/apps/dashboard.rst), the sandbox/urls.py and
expanded on the feature explanation on index.rst.

Fixes #816
Drop footer links

The About link was a 404 in a default sandbox installation because it
relied on a flatpage being existent. The Top of the Page link is bad UI
design, see #819 for an explanation.

Fixes #819
Update and re-enable template timings panel

It has been considerably improved and doesn't cause any significant
performance hit anymore. Hence, it's been enabled by default again.

@maikhoepfel also took the opportunity to re-order the DDT panels.

Fixes #820
Fix typo in promotions dashboard view
Remove urlencode that was missed previously
Fix broken links with page promotions
Tidy promotions dashboard template
Show breadcrumbs on flatpages page
Minor basket template changes

- Add breadcrumbs to summary page
- Don't use button for normal link
Simplify tagline
betwen -> between spelling mistake
Don't allow content blocks to link to external URLs

A recent change to the URL pattern means these don't resolve.
Adjust order of INSTALLED_APPS to help with custom migration

This helps when customising an app whose initial migration has
dependencies on other apps.  It's not a watertight fix but is backwards
compatible and will generally help.

Fixes #823