Sync with ovirt-engine 3.5 default theme

Because custom changes has been made in engine side based on
engine 3.5 default theme

Signed-off-by: walteryang <walteryang47@users.noreply.github.com>
Add styles and images for custom EayunOS login pages

Most of the styles are from:
https://github.com/eayun/EayunOS-homepage

Signed-off-by: walteryang <walteryang47@users.noreply.github.com>