[IOT-830] Added remove API for all credentials on |credresource|

[IOT-830] Added remove API for all credentials on |credresource|

added all credentials remove API for iotivity client with provisioning
feature. considering commercialization, iotivity client needs not only to
reset SVR data, e.g. doxm, acl and cred resources, but also to remove only
all credential data for its owned servers. for the former case legacy API(s)
could be supported but for the latter case additional API is needed.
the added API for this supports to remove all credentials and update
persistent storage in running iotivity client.
Jira-issue: https://jira.iotivity.org/browse/IOT-830

Change-Id: Icb41023f9acb6498c96e2b089a73daf4f39dd354
Signed-off-by: Kyungsun Cho <goodsun.cho@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4147
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: dongik Lee <dongik.lee@samsung.com>
Reviewed-by: Sachin Agrawal <sachin.agrawal@intel.com>