Refactor order input for comparable hashes

[j-ti]

Change cluster_index field to cluster_id
For the Order hash to be equivalent to the one accessible by the user both type of Order strings have to be equivalent:

• the integer field cluster_index should become a String field cluster_id.
  • also needs to be changed in simplyr-lib dependency
• to be clarified: should we integrate a field hash_version?
• to be clarified: we might add a salt of type Char with length=32 to create non-guessable orders