Add core privileges: usb.host and log

Add core privileges: usb.host and log

- usb.host: app can access to connected external USB devices
- log: app can access to platform log data
- both are platform level
- http://tizen.org/privilege/log is mapped to gid log
- http://tizen.org/privilege/usb.host is mapped to gid usb_device

Change-Id: I1726b463c077921071ff9b9f0348effe80ade38c
Signed-off-by: Yunjin Lee <yunjin-.lee@samsung.com>