[FileIO] Handler Sandbox URL for uploaded image files

[DonnaWuDongxia]

No description provided.

[DonnaWuDongxia]

With this method (use relative path default, and change them to sandbox URL), there is some resource reference error in console, because browser tries to fetch the resource taking the RIB directory as base path when serialize ADM to DOM. But, actually, the relative path is to project directory in sandbox, and they will be changed in design view and preview.
It will be good to suppress the browser to parse the DOM when serialize ADM to DOM. I haven't found way to do this so far.

[DonnaWuDongxia]

This pull request missing copying images when import, I'v got no time to complete it today. It will be done tomorrow.

[grgustaf]

Great work, very clean patches. I merged them all with slight style tweaks to the last patch.

I'll leave it open for today to make sure you see the comments. You can close it, or I will when I see it again.

[DonnaWuDongxia]

Thanks, Geoff! I close it now.