REPL for Ergo

[jeromesimeon]

We should provide a read-eval-print-loop for Ergo. This is useful for learning the language.

[jeromesimeon]

Some ideas for what the REPL could provide:

• Load existing Ergo files and CTOs and provide interactive loop
• Interactive execution:
  • Execute expressions and return results
  • Execute/test contracts with multiple parameters
  • Instantiate contract with its variables
  • Initialize a contract state
  • Calling a contract clause
  • Send a request to a contract
  • Respond with Error or Response + State + Emit
• Batch execution
  • Execute from a file
  • Use as test harness (e.g., as series of enforce?) to replace the smoke test (examples/smoke)
• Contract composition
  • Create a contract from multiple stand-alone clauses (e.g., new Contract{ } with clause1, clause 2