smb: urls support

[Manriel]

OS: Linux (Arch)
Software Version: 2.7.4

Application settings:
Configured connection to Transmission Daemon running on remote server by address 192.168.1.100 with download directory accessible by Samba share.
Directories mapping are:
local: smb://192.168.1.100/share/downloads
remote: /mnt/raid-drive/downloads

Action:

1. Right mouse click to downloaded torrent..
2. In context menu select "Open download directory"

Current behavior:
It show the warning:

Error opening smb://192.168.1.100/share/downloads/<torrent directory>.
The directory does not exist.

Expected behavior:
It opens samba share with address smb://192.168.1.100/share/downloads/<torrent directory> using default file manager application (or other app, configured to open smb:// url scheme).