Upgrade Express to 4.4.1

Want strong ETags.

See https://github.com/visionmedia/express/wiki/Migrating-from-3.x-to-4.x

Connect is no longer part of Express, so middleware is no longer on the
`express` object. Instead, we import the things (occasionally with new
names) and use those.
Fix indentation of 'Non-realistic dashboard'
Fix table display of unstacked device type graphs

5af264c33918c5a0c45932e7e46cd0bfce54935e changed existing dashboards
with "device type" graphs to use lines rather than stacked.

These line values are percentages, which needs to be reflected in the
axes configuration.

This changes the table display of this data from either '0' or '1' to
the actual percentage value.
Merge pull request #559 from alphagov/upgrade-express

Upgrade Express to 4.4.1
DVSA-dashboards-increase-period

increase report window to 26 weeks for digital take-up, completion rate and user-satisfaction
inserted agreed stages - change-practical-driving-test users-by-stage
changed completion rate calculation
Merge pull request #563 from alphagov/DVSA-dashboards-increase-period

DVSA-dashboards-increase-period
Add draft 'Register to vote' dashboard
Add first 3 modules to 'Register to vote'

- Live service usage
- User satisfaction
- Service availability
Merge pull request #561 from alphagov/73034886-fix-tables-unstacked-device-type

Fix table display of unstacked device type graphs
Add axisPeriod option to user satisfaction graph
Merge pull request #564 from alphagov/add-register-to-vote-dashboard

Add register to vote dashboard
Fix trim option on user satisfaction graph

The way you indicate that you don't want trimming is by setting
'trim' to false. Unfortunately, (false || true) is true, so you can
never disable trimming.

Be more explicit about checking the trim option for false.
Publish DVSA dashboards
Merge pull request #565 from alphagov/dvsa-user-satisfaction

DVSA user satisfaction tweaks
Add id to download section

I would like to send links which jump to the relevant part of the page.
Merge pull request #566 from alphagov/id-for-download

Add id to download section
New words on homepage
Add new about page

- Add new navigation
- Link to new /performance/about resource
- Skeleton HTML for Henry to put stuff in
Fix typo in routing
Update navigation links