Contract module which provides am implementation of Proxy pattern for upgradeable contracts.

This module is used through the embedding of proxy::Data and implementation of Proxy and Storage traits. It will allow us to update contract implementation via a Proxy pattern. We can get the current contract's implementation code hash or set the new implementation's code hash. To set a new code hash signer must be the owner of the Proxy.

The example consists of proxy, psp22_upgradeable and psp22_metadata_upgradeable contracts. The goal is to deploy proxy and psp22_upgradeable contracts, check that delegate calls through proxy contract to psp22_upgradeable work fine and then update contract to psp22_metadata_upgradeable.