do regular swap when baseFormID1,baseFormID2|swapFormID|etc

[NickStefan]

Add on to #10

After this PR the following examples should be true:

origBaseID,origBaseID2,origBaseID3|swapBaseID|propertyOverrides|chance
-> swaps all of the origBaseIDs with swapBaseID

origBaseID,origBaseID2,origBaseID3|swapBaseID,swapBaseID2,swapBaseID3|propertyOverrides|chance
-> randomly assigns each origBaseID to one of the swapBaseIDs

origBaseID,origBaseID2,origBaseID3|swapBaseID1,swapBaseID2|propertyOverrides|chance
-> logs an error. The swapBaseID set needs to either be a size of 1 or be equal/greater than the baseFormID set.

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Test case

[Forms]
; swaps everything left of `|` with an AlphaTest
BleakFallsTorchlight01,BleakFallsTorchlight01NS,BleakFallsDraugrTorch01,BleakFallsDraugrTorch01NS,BleakFallsCandleLight01,BleakFallsCandleLight01NS,BleakFallsDraugrTorch01Spot,BleakFallsDraugrTorch02,BleakFallsDraugrTorch02ns,BleakFallsDraugrTorch01NS_MoveLess,BleakFallsDraugrTorch01_HalfOmni,BleakFallsCandleLight01_Flicker,BleakFallsCandleLight01NSDesat,BleakFallsCandleLight01NSDesat,BleakFallsCandleLight01NSTESTTEST,BleakFallsDraugrTorchDesat01|AlphaTest

; randomly assigns swaps for so that each item left of `|` gets one swap from the right of `|`
DoomstoneWarrior,DoomstoneMage,DoomstoneThief,DoomstoneLady,DoomstoneApprentice,DoomstoneLover,DoomstoneSteed,DoomstoneAtronach,DoomstoneShadow,DoomstoneLord,DoomstoneRitual,DoomstoneTower,DoomstoneSerpent|DoomstoneWarrior,DoomstoneMage,DoomstoneThief,DoomstoneLady,DoomstoneApprentice,DoomstoneLover,DoomstoneSteed,DoomstoneAtronach,DoomstoneShadow,DoomstoneLord,DoomstoneRitual,DoomstoneTower,DoomstoneSerpent|NONE|chanceR(100,350)