Add iterators over all possibles parameters of a ParameterSet

For instance, you have two integer parameters
```
a in [1,3]
b in [2,5)
```
and the function would return
```
([1,2], [1,3], [1,,4], [2,2], [2,3], [2,4], [3, 2], [3,3], [3,4])
```
and we could generalize it to real parameters by providing a `Delta` between two numbers.

see also #26