Algorithmically find optimal step size

- Find the step size with the minimum maximum error, including all current and new amplitudes
- Remove messages warning about modifying all channels
- Add verbose error message when trying to apply stimulation parameters that will change the existing amplitude values
- Modified the GUI controls so that there is now a requested amplitude field, that the user can freely modify, and a readonly text box that displays the value that will be written to hardware
- This requested amplitude is also saved even if the step size changes to the point the amplitude is no longer valid
- If the step size changes and the requested amplitude is now valid again, it will be automatically applied, along with the original pulse timings
- Remove unused methods, remove unnecessary virtual identifiers
- Ensure that stimulus timings are correctly saved and applied automatically