simplify parameter-passing to ship history

-remove unused function for removal
-add and modify functionsm take a CShipHistoryStruct so that it's no
longer neccessary to construct shared CShips pointers
delete part of CShips::Scrap

I believe this is unneccessary, since those variables are cleared and
re-set at turn change anyway.
Don't grant credits and resources when building a starbase,

only when upgrading outposts or starbases.
It was like that until commit 8db88eacbbd3cdcd4be0be3e08e34a77f2b676d1
feature: upgrade command available also if it's due to a new special tech

Can't really test yet - should work.
unset SHIP_ORDER::DESTROY_SHIP when setting a target

I got caught in that a few times now.