Ensure height of find/replace fields are >= 22 points

Fixes #972.
Disable AuthorizationExecuteWithPrivileges deprecation warning

The “proper” replacement for this API is to use the ServiceManagement framework’s SMJobBless() to bless our helper tool. In two of the three use-cases our helper tool is however regular shell commands, so it seems redundant to wrap these shell tools as helper tools we can install as launchd
Remove redundant instance variable
Remove unused member data