Change BETA banner for HMRC manuals

- Removed Slimmer beta label
- Added Slimmer template
- Included govuk_component template
- Added handling for different Beta Labels for HMRC and non HMRC manuals

Removed slimmer settings for beta banner and added in handling for different manuals (hmrc and non hmrc) to have different banner text

Trello ticket: https://trello.com/c/Z2z8wKgh/432-hmrc-manuals-frontend-3
Merge pull request #114 from alphagov/Change-beta-banner

Change BETA banner for HMRC manuals
Remove .collapsible? check

There is no collapsiblity in hmrc manuals so remove this
Put content list in a list not h2

Before, when content was being displayed inline, these headers were h2s, but now these "headers" are actually links to pages, so remark-up these as a list of links. We can use the classes styled for the other type of manuals for this too.
Add styling for HMRC manuals to accommodate ids

HMRC manuals have section ids, so add (back) in styles for these, and display:table-cell/display:table-row to deal with flexible width of the ids

For mobile, stack the the id/title
Merge pull request #115 from alphagov/style-content-lists

Style content lists
Fix view logic for HMRC leaf nodes

As HMRC leaf nodes are now on the document.body, make sure they aren't accidentally made collapsible.
I'm not sure if it's possible for the HMRC API to give us a document with a `document.body` AND `document.section_groups` but it seems sensible to show them both if they're both there.

Non HMRC manuals should just have a `document.body` on their show action, but they don't need a don't need to be wrapped in a `.body-content-wrapper` class because their headings still need to be full width (as visually they are styled differently to hrmc's manuals)

Further work on this file (which I'm leaving here as a note for myself later) would be to remove:
`
<div class='title-controls-wrap'></div>
<div class='collapsible-subsections'>
`
and leave add the javascript to add in these elements as they are not needed unless the javascript is running.
Add width restricting CSS for body content

HMRC content and any body copy under a subsection now has this class to restrict it's width to two thirds on body copy
Add .body-content-wrapper class

This commit adds .body-content-wrapper to the javascript body copy, removing the body copy's width as a concern for the .js-subsection-body class.

This means HMRC manuals and regular manuals can share this class to share their width (and possibly other styles)
Merge pull request #116 from alphagov/fix-collapsibleness

Fix collapsibleness
Fix HMRC page titles

- Decapitalise Manual
- Add "internal"
Merge pull request #117 from alphagov/fix-page-title

Fix HMRC page titles
Remove bottom border from beta banner

The Beta banner has a grey 1px border which sits against the blue/green header in the manuals. As it is only 1px it makes the border look fuzzy so I'm removing it.
Merge pull request #118 from alphagov/remove-fuzzy-border

Remove bottom border from beta banner