[WIP] Support events watching from specific contracts

[AwaitFuture]

Problem:

• Lacked functionality listen to specific addresses for approvals

Solution:

• Add some logic to make handle it :^)

should solve most of #4

Open questions:

• I added a different config file I think is useful as a demonstration / interacting with test networks, let me know if I should remove it.
• These changes lack any testing; I intend to add some tests to at least confirm that the config parser produces the correct results, is there something else I should test aswell?
• address in log_subscription is forced into having empty string as the default case, which avoids doing any address specific logic. is there a better way to handle this? it seems necessary to at least have a default address value, since log_subscriptions ETS storage depends on it to distinguish between different log_subscriptions.

[AwaitFuture]

It seems like theres some transient failures on some tests; running individual tests seems to fail locally, but running all tests together causes them to pass most of the time. I looked through for a bit to see if I could sus out what is persisting from some test that allows all the others to pass, but Im not really sure.

[rupurt]

Thanks for the updates @AwaitFuture. I'll have to take a look at it locally

[AwaitFuture]

@rupurt I set the test blockchain in the runtime config to launch on start; somehow the poll interval for new heads gets set to nil if you do this sometimes. reverting that fixed it.