cgget: add the possibility to use -g <controllers>:<path>

cgget: add the possibility to use -g <controllers>:<path>

Most of the tools use <controllers>:<path> together with -g option,
this patch adds this version of usage of -g  option to cgget tool
Older have the possibility to use  -g in form -g <controller> <path>.

--------------
old version:
$ cgget -h
Usage: cgget [-nv] [-r<name>] [-g<controller>] [-a] ...<path> ...

new version:
$ ./cgget -h
Usage: cgget [-nv] [-r<name>] [-g<controller>] [-a] <path> ...
   or: cgget [-nv] [-r<name>] -g<controller>:<path> ...

Signed-off-by: Ivana Hutarova Varekova <varekova@redhat.com>
Signed-off-by: Jan Safranek <jsafrane@redhat.com>