Add attribute for graphic device

1. Modify base function place for grahic device use
2. Add attribute and element method for graphic

Signed-off-by: Kyla Zhang <weizhan@redhat.com>
Add new test for domdisplay

1. Add wrap in virsh.py
2. Add config file
3. Add test in src

Signed-off-by: Kyla Zhang <weizhan@redhat.com>