mainline examples

• bishoppawnpinrelation.cql
• castlerelation.cql
• echoflipvertical.cql
• enpassantrelation.cql
• enpassantrelationsymmetry.cql
• excelsior-multiple.cql
• knight-pawn-fork-relation.cql
• moved-black-piece-relation.cql
• queen-pawn-pin-relation.cql
• underpromotion-relation.cql
• virtual-mainline.cql
• white-try.cql
• wurzburg-plachutta.cql
• zugzwang1.cql
• zugzwang2.cql