Validate samples when creating boxes

[ysbaddaden]

When creating a box from selected samples, we should still do some validation based on the purpose:

1. Variant boxes created from samples should contain samples coming at least from 2 different batches;
2. Challenge boxes created from samples should at least contain one distractor and one non-distractor sample.
3. LOD and Other boxes created from samples don't need to more validation.

Follow up to #1867

[sardar-usman]

@leandroradusky The error message should be different as we have to add 2 different batches for Variant.

[sardar-usman]

@leandroradusky It is working fine now.