Write a simple ARG transfer test

[aybehrouz]

In this test we want to make sure that the balance of a user is checked before the transfer is performed. The test should perform this scenario: user A has 120 ARG. He issues two transactions to send 70 ARG and then 60 ARG to user B. First transaction should be successful but the second should fail. User A will have 50 ARG at the end.
The test should be added to this file:
ArgAppTest.cpp