real_fs_path in image select

[mipmip]

FUNCTION

• real path to image
• prefix path to add in json

EPIC

• [x] when opening and prefix path is set, this should be removed, and replaced by realpath before rendering
• [x] when saving image prefix path should be stored in json

CASE

• images could be added to assets (has other path)
• images could be added in static

[mipmip]

fixed in 018branch