[sugar] filename extensions not being shown by Journal

[Mikus Grinbergs]

A fellow-user suggested the following "hack" to differentiate in the 
Journal view between files 'foobar.txt' and 'foobar.pdf' (e.g., when 
those files were put onto a USB stick by a non-OLPC system):

Rename 'foobar.txt' to 'foobar.txt.txt', and 'foobar.pdf' to 
'foobar.pdf.pdf'.  Then Journal (in the current implementation) will 
display the respective entry names as 'foobar.txt' and 'foobar.pdf'.

mikus