Replace Some

Problem/Motivation

This module replaces all results of the search query and currently has no way to replace some.

Steps to reproduce

When on /admin/content/scanner, enter a search string and a replace string, and click "Replace".
Notice there's no way to limit what results are going to get replaced.

Proposed resolution

On the replacement confirmation page (/admin/content/scanner/confirm),
show the search results (same as the "Search" functionality on /admin/content/scanner),
add checkboxes (checked by default),
when the user clicks "Confirm", only replace the items that are checked.

Remaining tasks

* Add check/uncheck all button (all checked by default).
* Ensure tests still run.
* Perhaps add a test.
* Review by others.

User interface changes

The replacement confirmation page now always includes search results and checkboxes enabling the user to limit the replacements.

API changes

None

Data model changes

None