Implement ABI changes

[jasonpaulos]

Implement the changes described in algorandfoundation/ARCs#53

Additionally, the following implementation details should change:

• The atomic transaction composer should not add a group ID if there's only 1 transaction in the group, since it's unnecessary
• The atomic transaction composer should check that the type of a transaction argument (e.g. pay, axfer, etc.) matches the ABI transaction argument type.

[jasonpaulos]

Additionally, based on algorandfoundation/ARCs#57 and algorandfoundation/ARCs#55:

• The atomic transaction composer should allow app creation & update transactions to be made using the add_method_call method
• The composer should only check the last log for the return value
• Contract and Interface objects should have a description field

[algochoi]

Linked to #251