Clean up the "maintenance page" component in Bartik

Follow-up to #1342054: [META] Clean up templates and CSS →

Problem/Motivation

1. Bartik's template files need to be assessed and cleaned up of redundant markup, bad formatting and ID's.
2. Bartik's CSS files need to follow Drupal's

   ww.drupal.org/node/1886770">CSS Coding Standards.

Proposed resolution

For this issue we take "maintenance-page.css" within Bartik in css/maintenance-page.css plus any template file associated with the CSS and clean them up.

CSS formatting tasks to do

1. The CSS file needs to use the correct Comment formats - see guidelines here → and also reference other fixed Bartik CSS files for wording guidelines.

CSS architecture tasks to do

1. Replace any ID's with classes within the CSS files and Twig files associated with it - see guidelines here → .

CSS cleanup tasks to do

1. Check all of the selector rules are correct and are currently in use. Fix any broken ones found.

Remaining tasks

• Write a patch containing as much as the above as possible.
• Post a patch with screenshots.
• Visual review of a patch - check the Bartik Maintenance page visually with and without patch applied. Take screenshots.
• Code review of a patch - check the code follows coding standards, suggest improvements if needed in a comment.
• Produce a new patch with improvements if needed.

User interface changes

None

API changes

None

Data model changes

None

Beta phase evaluation