Remove unecessary references to "4.7"

Created by: seancolsen

This guide covers CiviCRM 4.7 and 4.6 with one branch.

(Note: there was originally a plan to use separate branches for master and 4.7, but after inspecting some content diffs I determined that using two branches is unnecessary because the content is basically the same.)

I based my migration on the 4.7 version of the wiki, so there are lots of places where pages mention 4.7 incidentally and in examples. I'd like to get rid of these occurrences, wherever possible, so that the guide is more "version agnostic".

I think we'll probably need to keep some of these references, but it'd be good to see which ones we can generalize a bit.