Add alert to admin page about old PHP version.

Add an alert message to admin summary page when a PHP version < 5.4 was
detected as this has reached EOL and will not be supported with the new
SabreDAV library.
Some styleguide optimisation.
Add NULL_DATE example to doc/sql_conventions.bb.
Display a "0" when no plugins active in summary page.
Added some more numbers to summary admin page, expired accounts,
channels. Hope I interpreted them right. I have no idea how to get
blocked accounts.

doc/sql_conventions.bb

@@ -56,7 +56,11 @@ $r = q("SELECT * FROM mail WHERE uid=%d AND $sql_extra ORDER BY created DESC LIM
 
 [b]NULL dates[/b]
 [li]To be written
-[code]Example[/code][/li]
+[code]// Example
+$r = q("DELETE FROM mail WHERE expires != '%s' AND expires < %s ",
+	dbesc(NULL_DATE),
+	db_utcnow()
+);[/code][/li]
 
 [b]Storing binary data[/b]
 [li]To be written

view/tpl/admin_summary.tpl

@@ -1,36 +1,32 @@
 <div class="generic-content-wrapper-styled" id='adminpage'>
 	<h1>{{$title}} - {{$page}}</h1>
-
+{{if $adminalertmsg}}
+	<p class="alert alert-warning" role="alert">{{$adminalertmsg}}</p>
+{{/if}}
 	<dl>
 		<dt>{{$queues.label}}</dt>
 		<dd>{{$queues.queue}}</dd>
 	</dl>
+	<dl>
+		<dt>{{$accounts.0}}</dt>
+		<dd>{{foreach from=$accounts.1 item=acc name=account}}<span title="{{$acc.label}}">{{$acc.val}}</span>{{if !$smarty.foreach.account.last}} / {{/if}}{{/foreach}}</dd>
+	</dl>
 	<dl>
 		<dt>{{$pending.0}}</dt>
 		<dd>{{$pending.1}}</dt>
 	</dl>
-
 	<dl>
-		<dt>{{$users.0}}</dt>
-		<dd>{{$users.1}}</dd>
+		<dt>{{$channels.0}}</dt>
+		<dd>{{foreach from=$channels.1 item=ch name=chan}}<span title="{{$ch.label}}">{{$ch.val}}</span>{{if !$smarty.foreach.chan.last}} / {{/if}}{{/foreach}}</dd>
 	</dl>
-	<!-- $accounts is empty
-		{{foreach $accounts as $p}}
-		<dl>
-			<dt>{{$p.0}}</dt>
-			<dd>{{if $p.1}}{{$p.1}}{{else}}0{{/if}}</dd>
-		</dl>
-	{{/foreach}} -->
 	<dl>
 		<dt>{{$plugins.0}}</dt>
 		<dd>
 		{{foreach $plugins.1 as $p}} {{$p}} {{/foreach}}
-		&nbsp;
 		</dd>
 	</dl>
 	<dl>
 		<dt>{{$version.0}}</dt>
 		<dd>{{$version.1}} - {{$build}}</dd>
 	</dl>
-
-</div>
+</div>