Change the subclass of range from widget to structure

This is needed to support the aria-value* attributes on non-interative,
and potentially static objects such as a meter.

Because range now subclasses structure, we need to use multiple inheritance
with the widget roles which subclass range. Those roles are: progressbar,
scrollbar, slider, and spinbutton. The latter two already subclass both range
and input thus no further change is needed. Progressbar and scrollbar now
subclass both range and widget.

Addresses github issue #892.

index.html

@@ -5161,7 +5161,12 @@ <h5>Presentational Roles Conflict Resolution</h5>
 					</tr>
 					<tr>
 						<th class="role-parent-head" scope="row">Superclass Role:</th>
-						<td class="role-parent"><rref>range</rref></td>
+						<td class="role-parent">
+							<ul>
+								<li><rref>range</rref></li>
+								<li><rref>widget</rref></li>
+							</ul>
+						</td>
 					</tr>
 					<tr>
 						<th class="role-children-head" scope="row">Subclass Roles:</th>
@@ -5401,7 +5406,7 @@ <h5>Presentational Roles Conflict Resolution</h5>
 		<div class="role" id="range">
 			<rdef>range</rdef>
 			<div class="role-description">
-				<p>An input representing a range of values that can be set by the user.</p>
+				<p>A structure representing a range of values that can be set by the user.</p>
 				<p class="note"><code>range</code> is an abstract role used for the ontology. Authors should not use this role in content.</p>
 			</div>
 			<table class="role-features">
@@ -5419,7 +5424,7 @@ <h5>Presentational Roles Conflict Resolution</h5>
 					</tr>
 					<tr>
 						<th class="role-parent-head" scope="row">Superclass Role:</th>
-						<td class="role-parent"><rref>widget</rref></td>
+						<td class="role-parent"><rref>structure</rref></td>
 					</tr>
 					<tr>
 						<th class="role-children-head" scope="row">Subclass Roles:</th>
@@ -5979,9 +5984,12 @@ <h5>Presentational Roles Conflict Resolution</h5>
 					</tr>
 					<tr>
 						<th class="role-parent-head" scope="row">Superclass Role:</th>
-						<td class="role-parent"><ul>
-							<li><rref>range</rref></li>
-						</ul></td>
+						<td class="role-parent">
+							<ul>
+								<li><rref>range</rref></li>
+								<li><rref>widget</rref></li>
+							</ul>
+						</td>
 					</tr>
 					<tr>
 						<th class="role-children-head" scope="row">Subclass Roles:</th>