Wip contract registry

[benjaminsalon]

Implementation of #60

Worked on top of #76 : only commits after contract registry first implementation, working for this PR.

To see how it needs to be implemented on the front end you can check in create-soroban-react preview:

• The getDeployments function which needs to be implemented, here using a json file
• The need to pass the deployments to the context here
• The call to useRegisteredContract here COMPARED to old way of getting contract address here
• The call to the wrapped invoke method directly on contract object here and here COMPARED to the old call here

[benjaminsalon]

@esteblock