"Editing Basics" first pass

I have more documentation/screenshots to add (covering things like the "Page" menu when editing a specific page, adding content/plugins, etc.) but this at least gets rid of the "TODOs" in the docs.
Google is very non-committal on this, their webmaster guidelines encourage setting this field by they reserve the right to choose their own title when displaying search results. Not sure what the best language to use would be but didn't want to mislead editors.