Display constraint weight and penalty in CQM

**Application**
I want to be able to see whether I set a hard or soft constraint on my CQM and what value of weight & penalty fo rsoft constraints.

**Proposed Solution**
Display as part of the `dimod.CQM.constraint`

**Alternatives Considered**
If that causes backward compatibility, maybe a new field. .

**Additional Context**
```
cqm1 = dimod.ConstrainedQuadraticModel()
a = dimod.Integer('a')
cqm1.add_constraint(a <= 3, weight=55, penalty="linear", label="Soft constraint")
cqm1.constraints["Soft constraint"]
```

Output ``Le(QuadraticModel({'a': 1.0}, {}, 0.0, {'a': 'INTEGER'}, dtype='float64'), 3)`` gives no hint of the type of constraint.