Don't show main menu until name is entered, references #2.

The GUI looks much cleaner now.
Reworked main menu interface, fixes #2, fixes #20.

 - added Options and Exit tabs
 - sorted elements into those tabs, which gives it an overall cleaner look
 - the tab bar no longer looks confusing. You know what si pressed at first
   glance
Added a mute button, fixes #10.