Document elevation/ascent/descent for filter (#26)

frontend/app/filter/filter-dialog.html

@@ -73,6 +73,12 @@
 				<td><code>symbol == &quot;accommodation_camping&quot;</code></td>
 			</tr>
 
+			<tr>
+				<td><code>ele</code></td>
+				<td>Marker elevation</td>
+				<td><code>ele &gt; 500</code></td>
+			</tr>
+
 			<tr>
 				<td><code>mode</code></td>
 				<td>Line routing mode (empty / <code>car</code> / <code>bicycle</code> / <code>pedestrian</code> / <code>track</code>)</td>
@@ -97,6 +103,12 @@
 				<td><code>time &gt; 3600</code></td>
 			</tr>
 
+			<tr>
+				<td><code>ascent</code>, <code>descent</code></td>
+				<td>Total ascent/descent of line</td>
+				<td><code>ascent &gt; 1000</code></td>
+			</tr>
+
 			<tr>
 				<td><code>routePoints</code></td>
 				<td>Line point coordinates</td>