[BUGFIX] Build links for accordion using Typolink (#335)

When the links are built using typolink, the full url is used for the anchor links.
This creates valid markup even when javascript is disabled.
Otherwise one would get redirected to the Homepage when clicking on an accordion tab.

Resources/Private/Templates/GridElements/Collapsible.html

@@ -3,7 +3,8 @@
 	<div class="panel panel-default {layoutClass} {alignClass}">
 		<div class="panel-heading" role="tab" id="heading-{data.uid}">
 			<h4 class="panel-title">
-				<a data-toggle="collapse" class="{f:if(condition: data.pi_flexform.data.columns.lDEF.expanded.vDEF, then: '', else: 'collapsed')}" data-parent="#group-{data.tx_gridelements_container}" href="#collapse-{data.uid}">{data.header}</a>
+				<f:link.page pageUid="#collapse-{data.uid}" absolute="1" class="{f:if(condition: data.pi_flexform.data.columns.lDEF.expanded.vDEF, then: '', else: 'collapsed')}"
+				additionalAttributes="{'data-toggle':'collapse', 'data-target': '#collapse-{data.uid}', 'data-parent': '#group-{data.tx_gridelements_container}'}">{data.header}</f:link.page>
 			</h4>
 		</div>
 		<div id="collapse-{data.uid}" class="panel-collapse collapse {f:if(condition: data.pi_flexform.data.columns.lDEF.expanded.vDEF, then: 'in', else: '')}" role="tabpanel">