Debugger: Flesh out option-based value editors.

TableCellOptionPopUpEditor:
- Add virtual hook for retrieving the final selected value. Implement
accordingly in Bool and Enumeration editor subclasses.
- Implement calling the edit completion hook upon value changes.

Debugger: Add interface subclasses for table cell editors.

TableCellTextControlEditor:
- Serves as a base for editors that expose their functionality via a
text control. Handles common functionality of watching for changes,
validating input, and notifying listeners appropriately.
TableCellOptionPopUpEditor:
- Serves as a base class for editors where the set of possible values
is fixed and known up front. Handles reacting to selection changes
and notifying listeners.

Debugger: Flesh out option-based value editors.

TableCellOptionPopUpEditor:
- Add virtual hook for retrieving the final selected value. Implement
accordingly in Bool and Enumeration editor subclasses.
- Implement calling the edit completion hook upon value changes.

Debugger: Add interface subclasses for table cell editors.

TableCellTextControlEditor:
- Serves as a base for editors that expose their functionality via a
text control. Handles common functionality of watching for changes,
validating input, and notifying listeners appropriately.
TableCellOptionPopUpEditor:
- Serves as a base class for editors where the set of possible values
is fixed and known up front. Handles reacting to selection changes
and notifying listeners.