ANW-975: Update to handle back button

[lorawoodford]

The additional of the select_all checkbox in #1726 can potentially have the unintended consequence of reloading a search listing page with individual checkboxes selected but the select_all box unselected. This forces autocomplete to off for the multiselect column inputs for search listing results to avoid this behavior if the user uses the browser's back button.

Description

This PR sets autocomplete to off for the multiselect inputs. It also ensures that multiselection will work on agents by including the multiselect js in agents.browse_merge.js (since agents does not natively inclue search.js).

Related JIRA Ticket or GitHub Issue

https://archivesspace.atlassian.net/projects/ANW/issues/ANW-975

How Has This Been Tested?

Tested manually.

Screenshots (if appropriate):

Improper behavior prior to this PR.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• I have authority to submit this code.
• I have added tests to cover my changes.
• All new and existing tests passed.