* Decouple logging and handling of distinct error messages for cases of
failed tx look up.
* This also fixes a bug wherein the `addrindexer` failed to lookup a tx
(since it didn't exist), but continued since the returned error was
nil.
* Address index is built up concurrently with the `--addrindex` flag.
* Entire index can be deleted with `--dropaddrindex`.
* New RPC call: `searchrawtransaction`
* Returns all transacitons related to a particular address
* Includes mempool transactions
* Requires `--addrindex` to be activated and fully caught up.
* New `blockLogger` struct has been added to factor our common logging
code
* Wiki and docs updated with new features.
