added funtion jo() to keep some javascript operators

  - the previous attempt was kind of troublesome, so i reverted some of the changes and moved them to a designated new function
  - the new function is called jo() (for "javascript operators") and can be used instead of id() to use some operators without quoting
  - there are some JS operators that aren't supported yet (like "++"). if i can figure out how to define them as dummy R operators first, that should change
  - things like "=" might never be possible, though