For constructors, now manage correctly:
- np array 0-rank arrays scalar,
- python int|float scalars,
- np scalars np.dtype() (different from 0-rank array scalars),
- contruction with dims=..., now a kw only argument,
- np arrays of rank >= 1 as before.

For setters, now manage correctly conversion without
loss of precision and do not raise in case of overflow as we
would expect with C++ interface.
Added support in ctors/get/set for some missing types, now
support [u]int(8|16|32|64).