Add account suspension features

Resolves T695

- Tagged posts
- Collection index

Ref T661

Some of the work needed to have the backend match user-facing wording.

Ref T661

This puts the verbiage more in line with what the feature does, and
leaves room for other moderation controls in the future.

NOTE: this includes no backend refactoring, which may be confusing. We
should rename things to fit ASAP.

Ref T661

From u.Status == UserSuspended to u.IsSuspended()

Ref T661

Previously, this had bad template logic and showed the wrong email address.

Ref T695

Ref T695

Also updates some whitespace in the JS.

Ref T695

This also adjusts the style and includes the user's password, so the
admin can easily notify them.

Ref T695

This resets user password to something random that also reminds the user
they should change it immediately after logging in, instead of a
completely random jumble of characters.

Ref T695

Move logic into template, rather than add another field to the page.

Ref T695

Ref T695

Fix URLs in CSV exports

the change to take a hostname in Post.CanonicalURL broke a few template
using that function. This adds a Hostname string to the Post being
passed to templates and passes it to calls to Post.CanonicalURL

This includes the instance's hostname in calls to export a CSV file and
PublicPost.CanonicalURL().

It also fixes a panic in that method during CSV export caused by draft
posts.

Previously it was above the header.

Ref T661

This also includes a bit of explanation about what suspending a user
actually does.

Ref T661

The link here is a little redundant, and might make people think that it
actually changes the status by clicking on it.

This adds a User.IsSuspended() method and uses it when displaying the
user's status on admin pages, instead of doing a magic number check.
This should also help in the future, in case this logic ever changes.

Ref T661

Default to user's first blog instead of draft.

Resolves T697

update IsJSON to check for Accept header

fix panic on duplicate remoteuser key

Now: Write.as Pro and Write.as for Teams

also fix logic bug in posts.go viewCollectionPost checking the page
owner

- update error messages to be correct
- move suspended message into template and include for other pages
- check suspended status on all relevant pages and show message if
logged in user is suspended.
- fix possible nil pointer error
- remove changes to db schema files
- add version comment to migration
- add UserStatus type with UserActive and UserSuspended
- change database table to use status column instead of suspended
- update toggle suspended handler to be toggle status in prep for
possible future inclusion of further user statuses

this adds a new button when viewing a user as an admin, that will
generate and store a new password for the user

add user invite instructions

Resolves T690

Ref T690

font-size-adjust is still a flag-enabled feature in Chrome 77, and
doesn't have widespread support across browsers. So instead this uses
font-size to make the text large enough.

Ref T690

This uses the Invite fetched from the database to explain a bit more
about how the invite URL expires. It also reduces some space around the
input box.

Ref T690

Ref T690

Ref T690

This ensures we see a 404 page when looking up an invalid invite URL,
even if the user is logged in.

Ref T690

check for lessc executable in any location

accidentally removed two lines from make all

fix check when trying to install lessc

this changes the helper IsJSON to take a request instead of a string,
allowing to check multiple headers. In this case both Content-Type and
Accept.