[2374][WebUI] Fix right-click selection issue
[#2310] [WebUI] Fix unicode password support
[#2343] Fix error if listen interface is whitespace

Whitespace in the interface dialog is not obvious to the user so
strip in core to prevent error from bad config
[#2082] Validate ip address for listen_interface entry

This ensures that only ip addresses are accepted for
listen_interface as libtorrent cannot accept interface
names (eth0) and will cause unexpected results for user.