A few bugfixes to the __repr__ methods of the reference classes.
A few bugfixes to the __repr__ methods of the reference classes.

* All such methods were printing as "Reference(...)" rather than the
  actual class name, which would defeat the purpose of the repr output.

* The authors were being printed without quotes around their names,
  which meant that the output was invalid Python syntax.

Both of these are addressed in this commit.

pierrelb/RMG-Py,KEHANG/RMG-Py,comocheng/RMG-Py,comocheng/RMG-Py,enochd/RMG-Py,pierrelb/RMG-Py,nickvandewiele/RMG-Py,nyee/RMG-Py,chatelak/RMG-Py,KEHANG/RMG-Py,nyee/RMG-Py,enochd/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,faribas/RMG-Py,faribas/RMG-Py