Add helical paths

Author: jes

bin/pngcam-go

@@ -88,6 +88,7 @@
                     <tr><td class="formlabel">Cut direction:</td><td colspan="2"><select id="direction">
                         <option value="horizontal">Horizontal (along X)</option>
                         <option value="vertical">Vertical (along Y)</option>
+                        <option value="helical">Helical (rotary only)</option>
                     </select></td></tr>
                     <tr><td class="formlabel"><div class="has-tooltip"><div class="tooltip">Perpendicular distance between consecutive passes.<br><img src="img/diagrams/stepover.png"></div></div>Step over:</td><td><input type="text" id="stepover"></input> <span class="unit-mm"></span> <div id="stepoverwarning" class="has-warning"><div class="warning">Step over should be smaller than tool diameter.</div></div></td></tr>
                     <tr><td class="formlabel"><div class="has-tooltip"><div class="tooltip">Maximum deviation of a flat surface, if cut by a ball-nose end mill with the given diameter and given step over.<br><img src="img/diagrams/nominaldeviation.png"></div></div>Nominal deviation:</td><td><span id="surfacedeviation"></span> <span class="unit-mm"></span></td></tr>