Get video edit fragment to look the same as view

Still need to refactor the GuideStepViewFragment to use Child fragments for
media the way that StepEditFragment does.
Fix off by one step number
Whoops, missed a fragment
Externalize video activity dialog strings
Clean up and fix resizing issues with guide thumbs

Resizing guide main images and thumbnails, as well as videos, was borked due to
some changes to ThumbnailView during the addition of Videos to guide create
steps. These changes solve that issue.

Also added the add image icon from the site instead of the overblown + icon