Space Marine Eradicators - allow minimum squad size of 3 when adding multi-melta

[sumo89]

This was tested on the Android app. The rules for Eradicators are that for every 3 models in the squad, one can upgrade their gun to a multi-melta. On the app this is achieved by adding a unit under the header "Eradicator with MM", but doing so now means the minimum squad size is 4 and you cannot reduce the amount of normal Eradicators below 2 (+ 1 reserved for Sgt).

[amis92]

Please move to https://github.com/BSData/wh40k

[sumo89]

Done, thanks.