Add Paste Delay option

Add Paste Delay option under Window, the same as TeraTerm has and other
SSH clients.

When staging configuration changes in notepad or whatever to then be
bulk pasted into an SSH session for a network device.. router, switch,
firewall, load balancer etc.. they don't like having 100+ lines of
config commands sent at them in one blast which putty does by default.
This result in some of the config lines being dropped or interpreted out
of order by the device.

This patch adds a new option which just sleeps for the specified
duration after each line break in the paste buffer, before sending.