Show price field Options that use disabled Financial Types so they can be edited.

When a financial type is disabled, there may be price field options or price fields that use the FT that no longer appear in some user interfaces even though they are enabled.

The problem is that price field options with disabled FTs cannot be viewed even on some admin forms in order to be selected for editing in order to change the FT.

Although it is not supposed to be possible, the system may allow FTs to be deleted, causing ON CASCADE Set NULL to set the FT for price fields or price field options to null. Fix system to prevent deletion of FTs that are in use by price fields or price field options.

Fix system to allow price field options that have null for FT or a disabled FT to be viewable and editable on admin forms, but not for backoffice creation of Contributions or Event Registrations or front office forms for purchases.