org.freeciv.action patch

Hello,

I wrote some patch which reorganises the (U)ACT actions using an 
ActionManager. Also made some changes to the creation of the MenuItems and 
replaced Olivier's KeyListener by a listener which seems more flexible to me.

Julian

PS: I hope the patch has the correct format because i've not made many 
submissions to projects like this. Please tell me if something isn't correct.

-- 
The only thing necessary for the triumph of evil is for good men to do 
nothing.
- Edmund Burke