conf: Support oom based event trigger and handler in conf

conf: Support oom based event trigger and handler in conf

Add 'MemoryLimitTrigger' conf to support oom based event trigger and handler.
If conf value is oom then, memory limit is handled by kernel oom. On the other hand,
reosurced handles memory limit directly with threshold value in the conf.

Change-Id: I785fc8bdac9505f990dc48cf3c4c7d4ead013c01
Signed-off-by: Unsung Lee <unsung.lee@samsung.com>