fixes types
- better coercion of tensors

- also:

1 : set(c,tensor(list(1,2,3,4)))
1=> mintegerTensor(list(1, 2, 3, 4))

2 : set(d,tensor(list(1,2,3,4.)))
2=> mrealTensor(list(1.000000000000000, 2.000000000000000, 3.000000000000000, 4.000000000000000))

3 : tensor(list(c,d))
3=> mrealTensor(list(list(1.000000000000000, 2.000000000000000, 3.000000000000000, 4.000000000000000), list(1.000000000000000, 2.000000000000000, 3.000000000000000, 4.000000000000000)))