process: Restore OOM_FIXED_APPS

process: Restore OOM_FIXED_APPS

The OOM_FIXED_APPS feature fixes the oom score of some applications
specified specified in the proc.conf file.

This feature was removed as follows(reverse chronological order):
    f6c9aab ("Support old style vip cgroup")
    ad81bd2 ("Rearrange memory cgroup")
    740d0f5 ("Rearrange optimizer configuration")
    f2b65a3 ("Update limiter.conf and support realtime")
    a3344a9 ("Support per app(service) management")
    574bf1b ("Add 'PerProcess' configurations")
    36a18bf ("Modify comments & remove useless things")

This feature has been restored by request.

Change-Id: I155a31722f1b5cae446663f690234faee0babe2c
Signed-off-by: SangYoun Kwak <sy.kwak@samsung.com>