refs https://github.com/TryGhost/Ghost/issues/8464
- fix padding on user actions button
- match user screen heading to other screens
- match app screen headers to other screens, update form styles
- change header link colour to match non-link colour
- fix team acceptance test
- fix canvas top padding so header elements always align
- reduce header font size
refs https://github.com/TryGhost/Ghost/issues/7865
- updates all settings screens to use EC tasks and `gh-task-button` to get save-state save buttons
- removes now-unused `settings-save` mixin
- moves the order of button color CSS so that grey buttons can change to green/red after completing
- removes the heading from `apps-loading` template so that there's no odd flash when loading slack/amp screens directly
no issue
- add loading substates for all routes that previously blocked transitions until their model had finished loading
- enables immediate response on navigation click
- loading templates include the title bar to provide immediate indication of which page is loading
- loading templates include a new `{{gh-loading-spinner}}` component that will only show the spinner after 200ms to avoid flashing a spinner for users on fast connections
- updated Version Mismatch tests to match new behaviour of intermediate transitions when navigating
