Add JSON data to Container.Config, specified with -j option of "run" com...

...mand  #439

Adds a field JsonMap to Container.Config.  The lxc_template uses data stored there to
augment the lxc config file.

The "run" command now has a "-j" command to specify the JSON object.

Currently only a "cgroup" field is supported.  It simply takes the key-value pairs from
the "cgroup" field (if exists) and emits  lxc.cgroup.key = value

Addresses issue #439