#7 Unknown hull identification optimization

[Ignacio Martínez]

Compared to VPA, JCV identifies less ship hulls in
starmap (maybe it is not using all the info in the
RST? no idea).

Apart from this, some hulls could be inferred from
previous turns in case the ship was previously
sigthed/hull identified. More accurate would be to
cross this info with a posible ship explosion after
the newest info refering to that ship.