Change calculation of mixed fleet bonus

http://www.forum.birth-of-the-empires.de./viewtopic.php?p=32531#p32531

* Change calculation of mixed fleet bonus from
"5% per ship type with a minimum ship count per ship type"
to
"1% per ship for the first five ships of a ship type"

* Change flagship bonus from 10% to 20%.

* Change commandship bonus from 20% to 10%.