Add repr method for cuqi samples

[chaozg]

• fixed Add method to display easy-to-read string for Samples object #468

Now when we evaluate/print a cuqi Samples, it will display something like:

CUQIpy Samples:
---------------

Ns (number of samples):
 2

Geometry:
 _DefaultGeometry1D(4,)

Shape:
 (4, 2)

Samples:
 [[ 1.38560564  0.53052923]
 [ 0.4737199   0.51313651]
 [-0.20398077 -1.29972158]
 [-2.48091298  0.27251739]]

[amal-ghamdi]

Thank you @chaozg for this nice addition :). I made a small comment here.

[nabriis]

Hey @chaozg. Thanks for working on these changes. I had some comments.

[amal-ghamdi]

Thank you @chaozg for the update. I have a small comment regarding the default geometry

[amal-ghamdi]

Thank you @chaozg, I like the updated print of the Samples object. And it is great that it is consistent with the CUQIarray print. Approved :)

[nabriis]

LGTM