Select all button for checkboxes on list of annotations on user-admin page

[RichardTaylor]

To make it easier for admins to remove spam add a select/deselect all buttons under the list of annotations on the user-admin page.

I'm noting this after I just clicked lots of checkboxes to remove a series of spam annotations.

I don't recall this being a regular problem.

Similar could be done for holding pen incoming message checkboxes; but there perhaps the extra step urges caution and properly checking each message before deleting it.

[RichardTaylor]

A work-round for administrators is creating a bookmarklet from:

https://stackoverflow.com/questions/10908212/select-all-checkbox-by-javascript-or-console

javascript:[].forEach.call(document.querySelectorAll('input[type="checkbox"]'),function(el){el.checked=true});

Bookmarking that link, then visiting it, checks all the checkboxes on a page.

[RichardTaylor]

An admin option to hide all annotations by the user is another way the underlying issue here could be addressed, perhaps more easily. (Selected annotations could then be made visible if desired).