DevDocs corrections part 1

Started reviewing the developer docs, finding lots of things to correct. I'll do more later, but please review this batch first so I know what, if anything, needs to be fixed moving forward - I'm not entirely sure on the markdownish format used.
I remember @harding used "generation transaction" before, and we agreed to switch to "coinbase transaction" after @mikehearn pointed out that "coinbase" seems to have become the standard lingo.