return config file options in getCmdLineOpts

Return another element with the config file options in addition to the direct command line options.

> db.runCommand("getCmdLineOpts")
{
"argv" : [
"/usr/bin/mongos",
"--logpath",
"/var/log/mongodb/mongos.log",
"--fork",
"--config",
"/etc/mongos.conf"
],
"/etc/mongos.conf" : [
....
]
"ok" : 1
}