Improve custom asset import error message#862

Every now and then a confused user posts on the forum about thousands of custom assets they had to import for a game to work.
In actual fact, they had faced the custom asset window that gets shown to them when a link is broken and clicked on the import button again and again, in eternal futility.
I therefore suggest to make the error message more visible and integrate it into the import window. The console tab is not sufficiently indicating that it has error messages relevant to what is shown on screen and new users who do not know about the game’s error reporting procedure will not understand what it means and draw the wrong conclusions, leading to frustration.
Also, please integrate a broken asset finder. The green outline currently present in the game is often not visible enough on complex table layouts.

See the attached file for a concept of how I imagine the window to look like.