refactor MathExpression to store errors and support updating epression
refactor MathExpression to store errors and support updating epression

ChristopherChudzicki/math3d,stardust66/math3d,ChristopherChudzicki/math3d,stardust66/math3d,stardust66/math3d,ChristopherChudzicki/math3d,ChristopherChudzicki/math3d,stardust66/math3d