open API improvements

• SelfDescriptionStutus schema introduced, to keep SD status definition in one place
• PageResult schema introduced for proper pagination handling
• Verification path: paths reduced to /verification
• SelfDescription path:
  • SelfDescriptions schema (extends PageResult) used to return readSelfDescriptions page results
  • String type used in response from readSelfDescription by hash method
  • 404 NotFound response added where it is expected
• Participants path:
  • Participants schema (extends PageResult) used to return getParticipants page results
  • UserProfiles schema (extends PageResult) used to return getParticipantUser page results
• Users path: UserProfiles schema (extends PageResult) used to return getUsers page results
• Session path: DELETE method used for logout
• Common fixes: camelCase schema used for schema attribute names

non-api changes:

• schemaManagement package renamed to shemastore to align with Java and project naming conventions