Add some docs about import and Hash algo
Add some docs about import and Hash algo

Describe which import uses which hash algorithm, or
how the hash algorithm during importing tokens seeds is
determined.

Closes #2257

privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea