Improve performance of purchasing parts and fix refit bug

[sixlettervariables]

While investigating an issue where ammo could not be bought, I noticed a number of huge performance slowdowns in the Purchase Parts screen. I also found a bug w.r.t. refit ID's.

1. Cache CurrencyManager::getDefaultCurrency. This was extremely expensive and called constantly 25bed25.
2. Remove text "sanitizing" from PartsInUse 21d2f0f.
3. Add Campaign::streamSpareParts and use it where allocating a huge ArrayList is unnecessary 51ffcd3.
4. Add Campaign::findSparePart to take a predicate to quickly find a matching part e8b0652.
5. Speed up AmmoStorage 43da701, Armor 72ce2f3, BaArmor b1c5751, ProtomekArmor c9fc5c5, and SVArmor a0ab221 bc100ad with findSparePart.
6. Speed up AmmoBin with findSparePart and streamSpareParts 18a608a. This one could use some eyes
7. Fix incorrect usage of reference equality of Refit ID's when value equality was intended a90d59b.

The time it takes to purchase 1000 units of AC/20 ammo by clicking 'Buy' is cut by ~70% on my desktop.

These commits are best viewed one by one with whitespace ignored (although I tried to minimize whitespace changes).