Make the missing data message in table modules span the full width

It looks nicer.

Also don't try to float the headers of really short tables (in particular, ones that contain only a no data message)
Updated tests to cater for how we now render "No data available"
Add filtering based on department title and abbreviation to services page
Don't escape HTML entities in link tags

We occasionally see 404 responses go out from Spotlight because
a client has made a request of ``GET /performance/&``.

I believe this may be because of the way Mustache is HTML-escaping
entities like this:

    <a href="&#x2F;performance&#x2F;carers-allowance">

In some clients, this might make a request matching the 404s we see,
because everything after the 2nd hash is treated as a fragment and
isn't sent to the server.

Anyway, just a theory. It's got some holes in it.

In any case, I think not HTML escaping the contents of href attributes
is the correct thing to do.

I'm going to make a similar pull request to alphagov/govuk_template
to address places this happens in the template.
Merge pull request #497 from alphagov/mustache-dont-html-escape-urls

Don't escape HTML entities in link tags
Merge pull request #494 from alphagov/feature/missing-table-data

Make the missing data message in table modules span the full width
Add deparment.abbr to required fields in dashboard schema

If a service has a department, than that department should have an abbreviation.
Used for filtering and catergorisation in the services page.
Merge pull request #496 from alphagov/feature/department-filtering

Add filtering based on department title and abbreviation to services page
Remove ymin config

this wasn't really actually doing anything useful. It was only used in sparklines, which were only used for real-time usage graphs. These always ended up with a min y value of 0, in the early hours of the morning, and it seems that we would always want these to be scaled from zero anyway.
Fix graph tests so they test what they say they do

Tests for "week" period were being config'ed with "day"
Also add tests for other applicable periods
Move `calculateLinearTicks` method from View into Graph

This is only relevant to graphs, and was only ever called from inside the Graph view.
Move methods from "overlay" config to graph as defaults

The default config for all graphs was overlay, so have the methods from that as default methods on a Graph instance, instead of extending at render-time.
Where those methods are not desired on child classes, extend in those isntances.
Remove last traces of overlay config
Add tests for new JourneyGraph calcYScale method
Extend line-label for stacked graphs instead of applying config madness
Move stacked graph functionality to stacked-graph view

Inherited from there for modules that require "stacked" functionality.
Prevent stacked graph from overwriting valueAttr option
Remove getConfigNames/applyConfig completely

Last remainin uses for these were to do period-based calculations for axes. Instead we replace the getConfigNames with a getPeriod method, and use this for period-dependent functionality.
Extend, rather than reimplement slightly different percentage graphs
Remove console log