api.c: Add options field for rules defined in cgrules conf file

api.c: Add options field for rules defined in cgrules conf file

This commit adds a fourth field called options to the rules
entry in cgrules configuration files.  Note that the field is
optional and existing rules will be parsed exactly as before.

Also, this commit only adds the parsing of the options field.
It doesn't change the rule behavior logic; that will come in
a subsequent commit.

An example cgrules.conf using this feature:

<user>    <controller>    <destination>           <options>
*         cpu             MyCgroup                ignore
*         cpu             DefaultCgroup

In the above example (and once the subsequent processing is
added), any process currently in the cpu controller and
MyCgroup will be ignored by cgrulesengd.  In other words,
cgrules will not try to move these processes to another cgroup
or manage them in any fashion.  It is anticipated that a
separate user process (outside of the scope of libcgroup) will
manage pids in this scenario.

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>