Changes:
0.13:
* add context menu "Add Host" in Connection Page.
* correct bug when clearing more than one donload at a time.
* better stop for downloads when quitting.
* avoid infinite lock in message treatment.
* limit some timeouts to 5 minutes.
* better stop for hash thread
* use hash for name of partial file, because thre is often two files with same name.
* avoid to display results with (null) hash.
* don't redisplay same file from same host in results
* added for stylesheet preview icons , its show in stylesheet combobox,
* some statistics computed : tot bytes downloaded, tot bytes uploaded, uptime.
* display this statistics in treeview and in graph.
* name of partial files is now hash+extension, because two different files can have same name.