Preserve source when using Number/RingElement +/- Matrix

Previously, if the number/ring element appeared first, then the result
was a matrix whose source *and* target was the target of the original
matrix

M2/Macaulay2/m2/matrix.m2

@@ -129,20 +129,20 @@ Matrix == ZZ := (m,i) -> if i === 0 then rawIsZero m.RawMatrix else m - i == 0
 Matrix + Matrix := Matrix => (
      (f,g) -> map(target f, source f, reduce(target f, raw f + raw g))
      ) @@ toSameRing
-Matrix + RingElement := (f,r) -> if r == 0 then f else f + r*id_(target f)
-RingElement + Matrix := (r,f) -> if r == 0 then f else r*id_(target f) + f
-Number + Matrix := (i,f) -> if i === 0 then f else i*id_(target f) + f
-Matrix + Number := (f,i) -> if i === 0 then f else f + i*id_(target f)
+Matrix + RingElement :=
+Matrix + Number      := (f,r) -> if r == 0 then f else f + r*id_(target f)
+RingElement + Matrix :=
+Number      + Matrix := (r,f) -> f + r
 Vector + Number := Vector + RingElement := (v,r) -> vector(matrix v + r)
 Number + Vector := RingElement + Vector := (r,v) -> vector(r + matrix v)
 
 Matrix - Matrix := Matrix => (
      (f,g) -> map(target f, source f, reduce(target f, raw f - raw g))
      ) @@ toSameRing
-Matrix - RingElement := (f,r) -> if r == 0 then f else f - r*id_(target f)
-RingElement - Matrix := (r,f) -> if r == 0 then -f else r*id_(target f) - f
-Number - Matrix := (i,f) -> if i === 0 then -f else i*id_(target f) - f
-Matrix - Number := (f,i) -> if i === 0 then f else f - i*id_(target f)
+Matrix - RingElement :=
+Matrix - Number      := (f,r) -> if r == 0 then f else f - r*id_(target f)
+RingElement - Matrix :=
+Number      - Matrix := (r,f) -> -f + r
 Vector - Number := Vector - RingElement := (v,r) -> vector(matrix v - r)
 Number - Vector := RingElement - Vector := (r,v) -> vector(r - matrix v)