Bump dependencies and drop Python 3.7 Support

This release upgrades the package dependencies to the latest versions and drops support for Python 3.7.

Introduce delegation proof type

• New Delegation Proof Type {DID, GENERIC}
• New API Proof objects: APIProof, APIDidDelegationProof, APIGenericDelegationProof used in advanced api
  (decouple api from crypto proof, deal with deleagtion proof type and content, backward compatible)
• New Advanced API helpers to create generic proof and allow delegation with generic proof
• New validation mode according to the proof type
• New Regisered document delegation proof type serialization

Fix documentation links

1.0.3

Fix relative links to github

Minor improvements

Make delegation_name parameter optional in high_level and regular APIs. If the parameter is omitted a random #name will be chosen.

Iotics DID Spec python implementation

Iotics DID Spec python implementation

• High level identity API/profile: a minimal set of features to interact with Iotics Host.
• Identity API/profile: set of features for identities management.
• Advanced identity API/profile: set of features for advanced identities management.