TSResourceSource fixes

This implements exception handling in the resource that was previously not being handled. The code for pulling data from the in_queue needed to be reworked to properly handle exceptions. A new flush_queue method is introduced to handle draining the queue while checking for resource exceptions.

Also:

• change the end property name to be end_time, to make it more accurately reflect the meaning, and to not confuse with the "start" method to start the sub-thread.
• remove unused parameter