refs ##8131
- "posts per page" is now a theme-level concern
- UI has already been removed, this finishes the cleanup by removing `settings.postsPerPage` and related validation/test support
closes https://github.com/TryGhost/Ghost/issues/8127
- update theme activation to manually set other themes to `active: false` in the store now that we only the active theme back from `/themes/:name/activate` endpoint
- move theme warning list item rendering into `{{gh-theme-error-li error=x}}`
- add `theme-warnings` modal that accepts a warnings list, title, and optional message
- after activating a theme, check if the theme has any warnings or errors and display an appropriate modal informing the user
requires https://github.com/TryGhost/Ghost/pull/8114
- adds "(Un-)Suspend User" options on user profile page with a modal confirmation screen
- separates team index into "active" and "suspended" users
- adds "suspended" badge to user profile when suspended
requires https://github.com/TryGhost/Ghost/pull/8093
- adds `theme.activate()` method and associated adapter method for activating themes rather than relying on `settings.activeTheme`
- minor refactors to the `modals/upload-theme` component to use a full theme model
refs TryGhost/Ghost#7860
- removes post type filter links
- adds dropdown filters for post type, author, and tag
- replaces custom refresh on query params change with Ember's standard `refreshModel` config
closes https://github.com/TryGhost/Ghost/issues/8055
- use `expired` if the date is in the past, otherwise `expires`
- fix mirage factories to use `moment.valueOf` instead of `moment.unix` for invite `expires` attributes
refs https://github.com/TryGhost/Ghost/issues/7860
- load 30 posts per page
- clean up unnecessary styles, match class name to component name
- start moving towards desired content/styles end goal
refs TryGhost/Ghost#7688
- Adds new upload functionality for a blog icon in general settings.
- Icons will be uploaded to a new endpoint `uploads/icons` to trigger different validations.
refs https://github.com/TryGhost/Ghost/issues/7860
- remove preview pane from content screen
- add basic post status filters
- replace custom infinite scroll with ember-infinity and increase trigger threshold for improved scroll behaviour
Commits:
* basic content list + filter using existing infinite scroll and pagination
* swap our custom pagination + infinite loader for `ember-infinity`
* minor cleanups
* reset scroll position when changing filter
* fix tests
* remove client-side sorting step as we no longer have a live collection
* remove unused `mobile-index-route`
* add acceptance tests for content screen filters
