Admin-UI: Allow for entry of Primary ID in create/edit modes if needed.

[CaMer0n]

Motivation

In some circumstances (eg. interacting with an API, instead of a database table) it may be necessary to enter the primary ID field when creating or editing a record using the Admin-UI.

Proposed Solution

Check for 'writeParms' => ['visible'=>true] in the field attributes before automatically hiding the primary id field or other special fields.
If found, do not hide the field in create or edit mode.

Also, an option to add a custom button above the list view layout (upper right) using renderCustomListButton() in the admin-ui form handler.