Change op to q.op for ANW-427

[lorawoodford]

Addresses issues discussed in the comments for #1128

Description

Changes "op" to "q.op" in default and example solr param config, and updates tests to reflect this change.

Related JIRA Ticket or GitHub Issue

https://archivesspace.atlassian.net/browse/ANW-427
https://archivesspace.atlassian.net/browse/ANW-762

Motivation and Context

Defaults staff-side search (including type aheads) to AND searches. This change does not impact public search.

How Has This Been Tested?

Passing backend tests, deveserver and built release behave as anticipated.

Screenshots (if appropriate):

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 updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.