Prevent admin from deleting email greeting, postal greeting or addressee format options if they are being used by one or more contact records

Deleting a greeting or addressee format when it's being used by contact record(s) causes data loss when the contact record is saved - AND it's difficult for the user to detect the cause of the problem because the cached (_display) value for the greeting or addressee is shown on the form and contact summary.

1. Check if the format is in use and block deletion w/ appropriate warning.
2. Warn on disabling of any option value - since disabling can have the same effect (this is true for most option values - e.g. prefix, suffix, gender, etc.).