add OCSetLogLevel API in logger

add OCSetLogLevel API in logger

we can filter log with level through setLogLevel API.
it will be helpped to reduce unnecessary log
without additional build option in some lite device.
and also we can filter private information such as Device ID,
Access Token, etc.

Change-Id: I91bff24737cbc7f09985adc142fc5f3d37e8f577
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17197
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>