Cardano part cleanup

[cleanerm5]

Description

As a Product Owner of the Cardano IBC implementation I want the Cardano side code base to be cleaned up to improve maintainability, portability/user experience and efficiency.

This should include the gateway and the smart contract part.

Scope/Acceptance Criteria

• The Aiken smart contracts have been reviewed and findings been implemented
• The on-chain code is in a shape that it can be executed in an economically feasible way
• The off-chain code has been adapted accordingly
• The Cardano gateway related code has been streamlined with regards to less dependencies, easy deployability and no hard wiring of configuration parameters in the source code
• The documentation has been updated accordingly