first pass on novice r reference sheet

addresses #663

First pass on the reference sheet.

almost just typed in any function/code I saw

Lots of work to do, but it's a start.
Typo: `form` -> `from`. (Note this doesn't remove *all* objects, just the visible ones). This is dangerous and I see many people including this in their scripts, even some SWC or other R instructors. This is truly bad form and instead we want to teach people to invoke clean R sessions to test their code/scripts. As such I don't think we need this.