ISPConfig3 Menu updates

[Polk]

Till,

I suggest rethinking the order of the main menu.
Make the order by the most used buttons.
When login have the selected button Sites and not emails. People manage sites more often than emails.

Make buttons in this order:

Sites, Clients, Emails, DNS, Monitor, System, Tools, Help

Notes:
Change Client to Clients, Email to Emails.
System should not be first button because once the server is configured, it's not used as often as Sites.