792: Implement crawl resumption

Task-Url: https://minfba.de.dariah.eu/mantisbt/view.php?id=792

collections/crawls.jsp

@@ -47,6 +47,9 @@
 								<c:if test="${crawl.state=='COMPLETE'}">
 									<button type="button" onclick="editor.performOffline('${crawl.id}');" class="btn btn-link"><i class="fa fa-repeat"></i> ~reindex</button><br />
 								</c:if>
+								<c:if test="${crawl.state=='ERROR'}">
+									<button type="button" onclick="editor.performOffline('${crawl.id}');" class="btn btn-link"><i class="fa fa-play"></i> ~ try continue</button><br />
+								</c:if>
 								<c:if test="${crawl.state!='INPROGRESS' && crawl.state!='QUEUE'}">
 									<button type="button" onclick="editor.removeCrawl('${crawl.id}', this);" class="btn btn-link"><i class="fa fa-trash fa-color-danger"></i> ~ remove</button>
 								</c:if>