Monitor transactions and/or blocks #12

Design and implement a RPC call to register a HTTP-JSON-RPC callback, and have it get called when blocks and/or "transactions of interest" occur.

Gavin has already implemented a version of this; unresolved issues are:

• How to specify which transactions are "of interest" ? Transactions to a specific address after A/B/C confirmations? All transactions to (or from?) the wallet? All transactions to (or from?) a specific account?

Note: information reported should be same as gettransaction.

• What information to report about blocks (if any). Perhaps implement a getblock before monitorblock.

Discussion here: http://www.bitcoin.org/smf/index.php?topic=2647.0

If debug.log showed full transaction IDs in the "got inventory" line, one could do:

tail -F debug.log | grep "got inventory.*new" | my-script

to monitor for new transactions and then run gettransaction to see the details. For some projects, this would be easier since no HTTP server is required. As it is, only partial transaction IDs are visible in debug.log so this doesn't work.

Suggested monitorblocks API posted to forum.

The current -blocknotify seems to take care of this. Addressing $IssueText directly, HTTP callbacks seem to have lost favor over program execution.