id: Add -d and -s options

These options may not be combined with any other options and print the
current or specified user's home directory and shell respectively.

Approved by: re (cperciva)
Reviewed by: imp, bcr
Differential Revision: https://reviews.freebsd.org/D53301

(cherry picked from commit f41b1eb637f576634be0df9d657f46aa57afea59)
(cherry picked from commit eff786f23611582e518f038e4086a1306c019d23)