Require blacklight 5.8+
Merge pull request #802 from sul-dlss/blacklight-5.8.0

Require blacklight 5.8+
Only remove the column if the column already exists
Merge pull request #803 from sul-dlss/759-fix-remove-migration

Only remove the column if the column already exists
Make sort-fields sortable and editable.
Add field target to edit-in-place so it doesn't rely on DOM placement.
Merge pull request #817 from sul-dlss/675-sort-config

Allow sort fields to be re-ordered and labels to be updated
Use sass-rails < 5 under rails <4.2