Refactor widgets

- Move widget templates to subfolder
- Add new generic filter widget templates to replace category, network and filer filters
- Update styles

src/Content/Widget/CalendarExport.php

@@ -59,7 +59,7 @@ class CalendarExport
 		// of the profile page it should be the personal /events page. So we can use $a->user.
 		$user = defaults($a->data['user'], 'nickname', $a->user['nickname']);
 
-		$tpl = Renderer::getMarkupTemplate("events_aside.tpl");
+		$tpl = Renderer::getMarkupTemplate("widget/events.tpl");
 		$return = Renderer::replaceMacros($tpl, [
 			'$etitle'      => L10n::t("Export"),
 			'$export_ical' => L10n::t("Export calendar as ical"),