Fix missing icon for open action in file list
Set placeholder text to torrent content filter.

In commit afb03725ad8fcf6eb1db305bdc89391a573f5968 it was implemented
for torrent list filter. Now it is here for files filter.
Set piece size to (max) 4Mb instead of empty string when created torrent
is very large.
Fix emptying of piece size combobox when user checks "auto" checkbox.

The function computePathSize returns -1 if file isn't found, not 0.
Merge pull request #2173 from sorokin/placeholder-text-torrent-list

Set placeholder text to torrent content filter.
Merge pull request #2174 from sorokin/fix-empty-combobox

Fix emptying of 'piece size' combobox when user enable 'auto' checkbox and no files are selected
Implement open & select file in file manager [Windows only]
Fix opening of samba shares
Merge pull request #744 from Gelmir/open_select

[Windows] Implement open & select file in file manager
Escape backslashes. Issue #800.