lock system wide encryption settings once the admin took a decision

apps/files_encryption/templates/settings.php

@@ -4,10 +4,10 @@
 	<strong>Choose encryption mode:</strong>
 		
 	<p>
-	<input type="radio" name="encryption_mode" value="client" style="width:20px;" <?php if ($_['encryption_mode'] == 'client') echo "checked='checked'"?>/> Client side encryption (most secure but makes it impossible to access your data from the web interface)<br />
-	<input type="radio" name="encryption_mode" value="server" style="width:20px;" <?php if ($_['encryption_mode'] == 'server') echo "checked='checked'"?> /> Server side encryption (allows you to access your files from the web interface and the desktop client)<br />
-	<input type="radio" name="encryption_mode" value="user" style="width:20px;" <?php if ($_['encryption_mode'] == 'user') echo "checked='checked'"?>/> User specific (let the user decide)<br/>
-	<input type="radio" name="encryption_mode" value="none" style="width:20px;" <?php if ($_['encryption_mode'] == 'none') echo "checked='checked'"?>/> None (no encryption at all)<br/>
+	<input type="radio" name="encryption_mode" value="client" style="width:20px;" <?php if ($_['encryption_mode'] == 'client') echo "checked='checked'"; if ($_['encryption_mode'] != 'none') echo "DISABLED"?>/> Client side encryption (most secure but makes it impossible to access your data from the web interface)<br />
+	<input type="radio" name="encryption_mode" value="server" style="width:20px;" <?php if ($_['encryption_mode'] == 'server') echo "checked='checked'"; if ($_['encryption_mode'] != 'none') echo "DISABLED"?> /> Server side encryption (allows you to access your files from the web interface and the desktop client)<br />
+	<input type="radio" name="encryption_mode" value="user" style="width:20px;" <?php if ($_['encryption_mode'] == 'user') echo "checked='checked'"; if ($_['encryption_mode'] != 'none') echo "DISABLED"?>/> User specific (let the user decide)<br/>
+	<input type="radio" name="encryption_mode" value="none" style="width:20px;" <?php if ($_['encryption_mode'] == 'none') echo "checked='checked'"; if ($_['encryption_mode'] != 'none') echo "DISABLED"?>/> None (no encryption at all)<br/>
 	</p>	
 	<p>	
 	<strong><?php echo $l->t('Encryption'); ?></strong>