ch07: add roles of sender and recipient

ch07.asciidoc

@@ -112,7 +112,7 @@ P2SH was developed to resolve these practical difficulties and to make the use o
 | Unlocking Script | Sig1 Sig2 <redeem script>
 |=======
 
-As you can see from the tables, with P2SH the complex script that details the conditions for spending the output (redeem script) is not presented in the locking script. Instead, only a hash of it is in the locking script and the redeem script itself is presented later, as part of the unlocking script when the output is spent. This shifts the burden in fees and complexity from the sender to the recipient (spender) of the transaction.
+As you can see from the tables, with P2SH the complex script that details the conditions for spending the output (redeem script) is not presented in the locking script. Instead, only a hash of it is in the locking script and the redeem script itself is presented later, as part of the unlocking script when the output is spent. This shifts the burden in fees and complexity from the sender (who creates the transaction) to the recipient (who unlocks and spends the transaction).
 
 Let's look at Mohammed's company, the complex multisignature script, and the resulting P2SH scripts.