Issue 514: Use Default Field 'df' to prevent syntax problems.

[kaladay]

Description

The behavior of manually adding the selected field as a string to the query causes problems. Instead, set the selected field as the Default Field 'df' in the query.

Fixes #514

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] Manually through the UI.
• [x] Ran unit tests.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] New and existing unit tests pass locally with my changes

[coveralls]

Coverage: 45.897% (+0.08%) from 45.813% when pulling 3d4bcccdd787a976dc235f36384aaa00a4a092fa on 514-silent_search_failure into 093cfbfb79de5d3ea8e7a223916edc18013ff98f on staging.