Improve manpower management

Give the player the choice of using or not manpower to build his ships for each system so we can focus manpower on ships we want to use to invade planets while we can avoid wasting it on exploration ships or ships used for defense and the like

After thinking about this i think the best way to have this to work is to have all ships created without any manpower, then while a ship is in one of your system, if you use the invasion comand you will be able to get a manpower management scrren allowing you to take troop in your ships or send them back to your system (if the system has full manpower it will send back to the empire reserves). This should allow much better gameplay (though it may add some micro management).

For instance many times during ellection i couldn't acess to the option intimidate population due to lack of manpower reserve even though i had much more than needed manpower in the ships orbiting my home system. Another interesting use would be when you have just conquered a system, you should be able to leave your troops there to defend it instead of taking everyone back to the ships.