Change "Unique title settings" to "Unique field settings"

Problem/Motivation

When I add a new field and want to configure it's unique settings the fieldset label is "Unique title settings" which is utterly confusing, because we are not making unique titles.

Steps to reproduce

Add new field to any entity, configure unique settings, label says "Unique title settings".

Proposed resolution

Change the label to "Unique field settings"

Remaining tasks

User interface changes

API changes

Data model changes