Switch RPC server to use fastsha256 package.
Bugfix for issue #101.
Update handleGetBlock to not use deprecated func.

Rather than using the deprecated TxShas function on a btcutil.Block,
convert handleGetBlock to use the newer preferred method of ranging over
the Transactions to obtain the cached hash of each transaction.

This is a little more efficient since it can avoid creating and caching an
extra slice to keep the hashes in addition to having the hash cached with
each transaction.
add importwallet to btcctl
Implement a rebroadcast handler.

This commit implements a rebroadcast handler which deals with
rebroadcasting inventory at a random time interval between 0 and 30
minutes.  It then uses the new rebroadcast logic to ensure transactions
which were submitted via the sendrawtransaction RPC are rebroadcast until
they make it into a block.

Closes #99.
Don't discuss internals in exported func comments.

This commit cleans up and moves a couple of comments in the recent pull
request which implements a rebroadcast handler (#114) in order to avoid
discussing internal state in the exported function comment.

How a function actually accomplishes the stated functionality is not
something that a caller is concerned with.  The details about the internal
state are better handled with comments inside the function body.
Kill duff newline.
simplify comment and fit into 80 cols.
Correct type capitalisation in comment.
comments - shorten, simplify and make 80cols.
Update websocket clients with rescan progress.

This change periodically (about every 10 seconds) notifies the
connected websocket client of the height of the last processed block
as part of the rescan.  This enables clients to listen for the
notification and keep track of how much progress a rescan has made
even without any results being found.  If the websocket connection is
lost during the rescan, on reconnect, clients may safely start over at
the last notified height.