Transactions Groups in Graviton

[tzaffi]

Lingering TODO from #21:

• Determine if dry runs can be made to handle transaction groups
• Determine if dry runs can be made to handle reference types and foreign references
• If the determination of the previous is "yes", enable graviton to handle such transaction groups + foreign references and then use to test abi methods with transaction/reference arguments. It should verify that when the expected pay / axfr / ... transactions are too far away (compared to the number of such args in the method signature and or foreign array) the program is rejected with error.