`ess-set-working-directory` with unescaped values of `default-directory` cause prematurely terminated strings, leading to unexpected symbol errors

```
> setwd('/home/bryce/src/echo/ECHO 'ChambeR' package/')
Error: unexpected symbol in "setwd('/home/bryce/src/echo/ECHO 'ChambeR"
```

The buffer-local value of `default-directory` used in `(ess-set-working-directory default-directory)`, in `ess-r-initialize` does not account for paths with quotation marks.