Pluralize Transaction In DevRef And DevPortal

Pluralize the Transaction header in DevRef and the links in DevPortal.  This is consistent with our usage in DevGuide and for other non-unique nouns when used as section headings.  (E.g. "block chain" is singular because there's only one (Bitcoin) block chain; "Wallets" is plural because there are many different wallets.  Thus "Transactions" should be plural because there are many different transactions.)