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

[bryce-carson]

> 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.