This makes this module's `GridFieldComponent` classes `Injectable`, and allows any future enhancements in the new abstract class to automatically apply without requiring additional changes in this module.
The class is introduced in silverstripe/framework 4.11.0 so the dependency constraint needs to be updated.
Also update docs to encourage use of dependency injection.
* Initialising button before attempting to enable or disable it
* Updating class reference
* Adding exception use case
* Removing unused use case
* Including Exception class for classes where exception is used.