This commit modifies the ChainNotifier interface, specifically the
ConfirmationEvent struct to now return additional details concerning
the exact location in the chain that the transaction was confirmed at.
This information will be very useful within the new routing package, as
within the network, channels are identified via their channel-ID which
is a compact encoding of: blockHeight | txIndex | outputIndex
This commit updates the documentation for the ChainNotifier interface
to specify that all implementation MUST be able to support dispatching
the same notification to multiple clients.
This commit refactors the existing chainntnfns package in order to
allow more easily allow integration into the main system, by allowing
one to gain access to a set of end-to-end tests for a particular
ChainNotifier implementation.
In order to achieve this, the existing set of tests for the only
concrete implementation (`BtcdNoitifer`) have been refactored to test
against all “registered” notifier interfaces registered. This is
achieved by creating the concept of a “driver” for each concrete
`ChainNotifer` implementation. Once a the package of a particular
driver is imported, solely for the side effects, the init() method
automatically registers the driver.
Additionally, the documentation in various areas of the package have
been cleaned up a bit.
