Add a key shortcut to "Add link to torrent..."

"Ctrl-Shift-O" will open the "Add link to torrent..." window.
Strip some png to fix incorrect sRGB profiles.

libpng complained about incorrent sRGB profiles in some png's.
"libpng: iCCP: known incorrect sRGB profile".
Merge pull request #1060 from alderz/master

Add a keyboard shortcut to "Add link to torrent" and fix some png sRGB profiles.