Update documentation with new waveform names

gui/index.html

 		<ul>
 		<li><span class=literal>WAVEFORM_SINE</span></li>
 		<li><span class=literal>WAVEFORM_SAWTOOTH</span></li>
+		<li><span class=literal>WAVEFORM_SAWTOOTH_REVERSE</span></li>
 		<li><span class=literal>WAVEFORM_SQUARE</span></li>
 		<li><span class=literal>WAVEFORM_TRIANGLE</span></li>
 		<li><span class=literal>WAVEFORM_ARBITRARY</span></li>
 		<li><span class=literal>WAVEFORM_PULSE</span></li>
+		<li><span class=literal>WAVEFORM_SAMPLE_HOLD</span></li>
 		</ul>
 	</p>
 </script>