Add the ability to re-map non-classified data set fields

[T-Dnzt]

Overview

Add the ability to re-map non-classified data set fields by displaying links to the mapping page and adjusting the mapping & analysis logic.

Type of change

• [X] New feature (non-breaking change which adds functionality)

Related tickets

Fixes #88

Changes

• Add links to the mapping page on the data set index page, show page, and edit page.
• Adjusted the mapping logic to allow the re-mapping of fields without any classification.
• Disable the mapping selection for fields that have classifications and disable the options mapped to classified fields for all other fields.
• Allow a data set to be analyzed more than once (with a check to avoid re-analyzing the same fields)
• Destroy all unique_values if the new common_type is not of interest (i.e. not part of Field::VALUE_TYPES)

Notes