implement the cmdline for COLO

implement the cmdline for COLO

Add a new option -c to the command 'xl remus'. If you want
to use COLO HA instead of Remus HA, please use -c option.

Update man pages to reflect the addition of a new option to
'xl remus' command.

Also add a new option --colo to the internal command 'xl migrate-receive'.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Yang Hongyang <hongyang.yang@easystack.cn>
Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>