View strings differ from GAP

Compare
```
gap> HomalgMatrix( [ 1, 0, 0, 0,  0, 1, 0, -1, -1, 0, 2, 1 ], 3, 4, HomalgFieldOfRationals( ) );
<A 3 x 4 matrix over an internal ring>
```
to
```
julia> HomalgMatrix( [ 1, 0, 0, 0,  0, 1, 0, -1, -1, 0, 2, 1 ], 3, 4, HomalgFieldOfRationals( ) )
[ 1//1   0//1   0//1    0//1]
[ 0//1   1//1   0//1   -1//1]
[-1//1   0//1   2//1    1//1]
```