Linux: icon filenames are case-sensitive

[SaphireLattice]

After a dirty hack of .replace("\\","/") to make it actually find files, i found out that some icon files are not loaded because they are not found.. And the reason for that was that the filename in the .dm file used different case than the actual file. Of course, if there are multiple files with same name but different case, it might get messy.. But this is still a problem.

[ghost]

#14 should resolve the first part of this issue.