Add PEM support to credential publicData

Add PEM support to credential publicData

Change-Id: Id5bfd6b1a08c295b49981bd7b938ec5d23522db4
Signed-off-by: Andrii Shtompel <a.shtompel@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/15945
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jongsung Lee <js126.lee@samsung.com>
Reviewed-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>
(cherry picked from commit 33a394c80fa6427e541654fb9ce763ec6f750534)
Reviewed-on: https://gerrit.iotivity.org/gerrit/16429