Add function to load a contract from directory/file

[nielstron]

A function that simply tries its best to load a contract and choosing the correct action based on being passed

• a Plutus blueprint
• a script.plutus json file
• a script.cbor singly wrapped cbor hex
• a script.addr script address
• a script.policy_id policy id
• a directory containing any of the above artifacts

Context

Avoids problems like #240

OpShin just creates a folder like the above

Same as OpShin/opshin#123, ideally no code duplication required.