v3.5 errors fix

Hi braekling,

on the network admin stats page for wp-piwik (http://wp-network.tld/wp-admin/network/index.php?page=wp-piwik_stats) are 2 warnings:

1st:
Warning: Missing argument 2 for wpdb::prepare(), called in /var/www/clients/client2/web8/web/wp-content/plugins/wp-piwik/settings/sitebrowser.php on line 40 and defined in /var/www/clients/client2/web8/web/wp-includes/wp-db.php on line 990

2nd:
Warning: Missing argument 2 for wpdb::prepare(), called in /var/www/clients/client2/web8/web/wp-content/plugins/wp-piwik/settings/sitebrowser.php on line 41 and defined in /var/www/clients/client2/web8/web/wp-includes/wp-db.php on line 990

— Fix: https://make.ww.wp.xz.cn/core/2012/12/12/php-warning-missing-argument-2-for-wpdb-prepare/

on the wp-piwik stats page for individual sites in a network is the following notice:

Notice: Undefined variable: bolNetwork in /var/www/clients/client2/web8/web/wp-content/plugins/wp-piwik/wp-piwik.php on line 1113

no real problems on 3.5 so far

http://ww.wp.xz.cn/extend/plugins/wp-piwik/