SmrShip: simplify weapon reordering methods
SmrShip: simplify weapon reordering methods

Use standard array functions to swap, rotate, add, and remove weapons
from the `weapons` array. This streamlines the methods `removeWeapon`,
`moveWeapon{Up,Down}`, and `addWeapon` (replacing the clunkier for-
loops and temporary variables used previously).

hemberger/smr,smrealms/smr,hemberger/smr,hemberger/smr,smrealms/smr,smrealms/smr,hemberger/smr