Untag pages that aren't in the user-centred-design section
Remove surplus index pages and rename breadcrumbs
Move 'Intro to user research' page intro 'user-research' folder as index page and update referring links
Only show 'More guides' header if there ARE more guides to show
Fix breadcrumb
Rename and update Data-driven services session

formerly KPIs: setting the bar
Throw away the "key"

Use vital instead as recommended by @fatbusinessman
Clarify SSL verification process

This commit clarifies the SSL verification process used when a service
domain needs the infrastructure team to verify a domain.
Enhance linting

Capture column as well when we spot a problem.
Typo
Merge pull request #392 from alphagov/feature/lint-error-messages

Enhance linting
Extract function
Format error message for easier readability

```
Bad Markdown URL in service-manual/agile/features-of-agile.md:
extra closing bracket at line 30, column 27
Bad Markdown URL in service-manual/agile/features-of-agile.md:
extra closing bracket at line 32, column 19
```

compared with

```
Bad Markdown URL in service-manual/agile/features-of-agile.md:
	extra closing bracket at line 30, column 27
Bad Markdown URL in service-manual/agile/features-of-agile.md:
	extra closing bracket at line 32, column 19
```
Update header screenshots for new alpha/beta style

The alpha/beta banners were updated in alphagov/govuk_frontend_toolkit@e295f45f59495f8e37e37a105da6d9d8b2695a54,
so redo the screenshots with those new styles.

See also: https://github.com/alphagov/govuk_frontend_toolkit/pull/112
Merge pull request #393 from alphagov/update-alpha-beta-banners

Update header screenshots for new alpha/beta style
Merge pull request #388 from alphagov/change-https-details

Clarify SSL verification process
ICT Spend Control Form version removed on Cabinet Office request
Merge pull request #395 from alphagov/spending-controls-

ICT Spend Control Form version removed
Rewrite guidance and update examples

Conflicts:
	service-manual/assets/images/header-footer/header-pattern-1.png
	service-manual/assets/images/header-footer/header-pattern-2.png
	service-manual/assets/images/header-footer/header-pattern-3.png
Update example border style

Conflicts:
	service-manual/assets/stylesheets/design-patterns/_help-popup.scss
	service-manual/assets/stylesheets/helpers/_examples.scss