improve error message for sx rawscript
move validtx into BLOCKCHAIN QUERIES category
Unify wording for BLOCKCHAIN UPDATES commands. Help now reads

BLOCKCHAIN UPDATES
   bci-pushtx                 Send tx to blockchain.info/pushtx.
   broadcast-tx               Send tx to bitcoin network.
   ob-broadcast-tx            Send tx to obelisk server.
   sendtx                     Send transaction to a single node.
move showscript into TRANSACTION PARSING
consolidate CREATE TRANSACTIONS category
move showblkhead out of BLOCKCHAIN QUERIES, now BLOCKCHAIN QUERIES is truly all commands that touch the network
finish consolidating CREATE TRANSACTIONS category