certificates: switch default page to certificates

This one is used more frequently and also expected when one
clicks on a link that says `Certificates'.

src/opnsense/mvc/app/models/OPNsense/Base/Menu/Menu.xml

 <menu>
     <!-- Core menu system including legacy stuff -->
     <System order="0" VisibleName="System" cssClass="glyphicon glyphicon-dashboard">
-        <Certificates url="/system_camanager.php">
-                <CertificateAuthority VisibleName="Certificate Authority" url="/system_camanager.php"/>
+        <Certificates url="/system_certmanager.php">
                 <Certificates url="/system_certmanager.php"/>
+                <CertificateAuthority VisibleName="Certificate Authority" url="/system_camanager.php"/>
                 <CertificationRevocation VisibleName="Certification Revocation" url="/system_crlmanager.php"/>
         </Certificates>
 

src/www/fbegin.inc

@@ -126,7 +126,7 @@ function active_main_menu() {
 
 // System
 $system_menu = array();
-$system_menu[] = array(gettext("Certificates"), "/system_camanager.php");
+$system_menu[] = array(gettext("Certificates"), "/system_certmanager.php");
 $system_menu[] = array(gettext("Firmware"), "/system_firmware_check.php");
 $system_menu[] = array(gettext("High Availability"), "/system_hasync.php");
 $system_menu[] = array(gettext("Routing"), "/system_gateways.php");

src/www/system_certificates_tabs.inc

@@ -3,8 +3,8 @@
 $active_tab = isset($active_tab) ? $active_tab : $_SERVER['PHP_SELF'];
 
 $tab_array = array();
-$tab_array[] = array(gettext("Certificate Authority"), $active_tab == "/system_camanager.php", "system_camanager.php");
 $tab_array[] = array(gettext("Certificates"), $active_tab == "/system_certmanager.php", "system_certmanager.php");
+$tab_array[] = array(gettext("Certificate Authority"), $active_tab == "/system_camanager.php", "system_camanager.php");
 $tab_array[] = array(gettext("Certificate Revocation"), $active_tab == "/system_crlmanager.php", "system_crlmanager.php");
 
 display_top_tabs($tab_array);