use boost::ptr_vector for wesnothd::game::history_
use boost::ptr_vector for wesnotd::server::games_

this way we have a prettier interface and don't have to delete them
manually.

I also had to change some functions that previously took non-null
pointer to taking referenes.
Merge pull request #340 from gfgtdf/wesnothd_sides

use boost::ptr_vector for wesnothd::game::history_
use boost::ptr_vector for wesnotd::server::games_