Closes #107

Implement the KMIP operations SetAttribute and DeleteAttribute:

• on server:
  • these 2 operations are unitary (1 single attribute is set/deleted)
  • not all attributes can be set (there are a lot but main attributes can be (algo, links especially)
• on ckms:
  • add 2 actions:
    • SetAttributes and DeleteAttributes (multiple attributes being possible)
  • test on every possible values of attributes
  • in get_attributes:
    • replace the struct AttributeTag by the KMIP tag struct to simplify/make more generic and make easier the get-attributes evolution
    • all links can be retrieved and also filtered if needed with the new action-parameter ckms get-attributes --link-type
• on kmip crate:
  • make clap-compliant enums ObjectType, KeyFormatType, CryptographicAlgorithm, LinkType and Tag
  • then can be used directly in ckms args