wish: fix the menu structure (minor)

[Maciej Pilichowski]

Hello,

  Currently there is "duplicate window" function in "location" menu, 
and "duplicate tab" in "window" menu which is quite confusing and 
counterintuitive. My suggestion is to move all items related to 
"tab/window" to "window" menu (new window, new tab, duplicate 
window), while keeping all items related to current location in 
"location" menu (no changes).

have a nice day
bye