fixes following issues:
* F3/F4 on 'del' and 0-length files works, however it is impossible to change 'del'
files (cached content can be confusing)
* Koala files and other with non-ASCII characters are supported (implemented directory
reading routine in pure python - for now only D64 format is supported)
* Added workaround for filenames with space at the beginning (however, as it was stressed
before, it is more generic issue than this script. Maybe it is good idea to use pcre
instead of iterating and splitting?)
* minor bugfixes and code cleanup
Signed-off-by: Slava Zanko <slavazanko@gmail.com>