[Seaside] Grease - get image directory

[Francois Stephany]

Hi,

GRPlatform has two methods: filesIn:aPathString and 
directoriesIn:aPathString. They return the absolute paths of the 
contained files.

However I do not see any (portable) way to know the image directory.

I think it is sometimes needed, for example:
GRPlatform current directoriesIn: 'bootstrap'

(where bootstrap is a directory next to my Pharo image). Gives me all 
the absolute path of the directories lying in <image directory>/bootstrap

How can I get the relative path of these directories compared to the 
'bootstrap' directory?

Cheers,
Francois