client: add a convenience function to destroy a queue

Signed-off-by: David Scott <dave.scott@citrix.com>
Add a 'Client.disconnect' operation to close client connection(s)

Signed-off-by: David Scott <dave.scott@citrix.com>
server: add 'shutdown' function

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #14 from djs55/async

Add 'disconnect' and 'shutdown'