NO-JIRA: Added tutorial/sync_client.py to demonstrate a synchronous request-response client.

This client uses the familiar paradigm of making blocking calls that send a
request and return the response.

Made some improvements to BlockingThread error handling and timeouts.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/examples@1626029 13f79535-47bb-0310-9956-ffa450edef68