Bugfix create_pdfs stdout writing with no info

* When create_pdfs is run without a long org or long_course configured,
  their values were None, which would cause the stdout report writer to
  blow up. This defaults them to empty string, which can be printed
  nicely.

* Change the randomized title assignment flag to be -T which is more
  mnemonic

* Reassign the -R flag to generate no report at all, even one to stdout

@stvstnfrd and @sarina 

This started because I ran create_pdfs on a course without long_course or long_name set and the report generation blew up. In fixing that, I realized that it would be nice to be able to toggle it off, and the most obvious flag to use for that was -R, which meant changing the titling flag... (which, as far as I can tell, nobody else ever uses.) I think this is all pretty inoccuous.
Symmetry, mostly, and the fact that when I was testing something using create_pdfs I actually didn't want a summary report at all; I just wanted the PDF location information it prints as a side-effect.