Finish up post count support in tags API

Refs #4521
- Handle 'include' query param in tags API.
- Add post_count support when fetching a tag with findOne.
- Remove post_count from options.include after processing.
- Extra database query no longer used to fetch post_count.
Add a URL preview componant

Closes #4499

- Introduces a URL preview component
- Added the component to tag settings and post settings
- Adds a new CSS file for this component which makes sure the preview never wraps onto multiple lines
Add tests to verify db version hasn't changed

issue #4479

- these tests will need updating if ever the db schema (not inc validations), permissions fixtures or db
version ever changes
- the intention is that it is no longer possible to accidentally change permissions or the db schema without
knowing you need to update the db version and the values in this test file
Merge pull request #4686 from jaswilli/tag-api-post-count

Finish up post count support in tags API
Merge pull request #4546 from PaulAdamDavis/url-preview-comp

Add a URL preview componant
Merge pull request #4688 from ErisDS/migrate-test

Add tests to verify db version hasn't changed
Updated meta helpers to use tag meta data if present

No issue

- Tag Meta title and description override default response
- Tag Meta title present on all pages
- Tag Meta description available only on first page
 - Updates tests
Fix broken user list paginated scrolling

Closes #4695

- Adds a new class to the template and minor CSS to allow user list scroll events to work
Merge pull request #4696 from PaulAdamDavis/paginated-users-scroll

Fix broken user list paginated scrolling
Updated tag management UI with the post counts

closes #4683
- added post count to 'delete tag' modal
- fixed lint errors
- preventing extra data to be sent to server
- adjustments suggested by @jaswilli
Run tag add operations in sequence

Closes #4697
- Run tag add operations in sequence instead of in parallel
  since generateSlug will hand out duplicate slugs until one of
  them is committed to the database.
- Add test.
- Misc cleanup of method parameter names and jshint hints.
Merge pull request #4689 from ekulabuhov/4683_TagPostCountUI

Updated tag management UI with the post counts
Finish tag post count UI.  Misc tag related fixes

Issue #4683
- Finish setting up pagination in tag management page.
- Add post count warning to delete tag modal.  Fix styling.
- Make sure tag input menu is loading all tags.
- Only include saved tags in tag input suggestion list.
- Unload tag records from store when entering tag route so that
  we get accurate post count.
- Add a resetPagination action to pagination-controller-mixin for
  cases where we want to start fresh.
- Include tag.id when sending tag payload to API.
Merge pull request #4693 from cobbspur/metatags

Updated meta helpers to use tag meta data if present
Merge pull request #4698 from jaswilli/tag-dup-slugs

Run tag add operations in sequence
Fix back button on tag UI page

closes #4703

- previous link used absolute url which fails for subdirectories
Merge pull request #4704 from cobbspur/tagsbutton

Fix back button on tag UI page
Merge pull request #4699 from jaswilli/issue-4683

Finish tag post count UI.  Misc tag related fixes
Fix modal edge spacing

No issue

The transparent border surrounding modals was being cut off.
This fix uses padding instead of adjusting the left & right valued to create space.
Fix tag mgmt display bugs

- Misaligned header due to back button being in the wrong place in the markup
- Corrected padding on tag delete button
- Updated tag settings input labels for consistency