Set to None if no value provided
Set to None if no value provided

* Add a method to set the configuration variables to None if the
  configuration values are not provided at startup or in the
  configuration files.
  The system already checks for these values, and if they are absent, it
  simply fails to display the OAuth service as available for use to
  login.

pjotrp/genenetwork2,zsloan/genenetwork2,pjotrp/genenetwork2,DannyArends/genenetwork2,pjotrp/genenetwork2,DannyArends/genenetwork2,pjotrp/genenetwork2,pjotrp/genenetwork2,genenetwork/genenetwork2,genenetwork/genenetwork2,DannyArends/genenetwork2,genenetwork/genenetwork2,DannyArends/genenetwork2,zsloan/genenetwork2,zsloan/genenetwork2,DannyArends/genenetwork2,zsloan/genenetwork2,DannyArends/genenetwork2,genenetwork/genenetwork2