* fixed issue of getting http 409 conflict errors when logging large amounts of data

(removing possible duplicate rowkey + partitionkey issue). I am getting hundreds of http 409 conflict errors from azure table storage per day because the current rowkey + partitionkey implementation does not guarantee that collisions won't occur due to timing issues. The partitionKey prefix won't help since I am logging only 1 application (same prefix), but tens of instances and thousands of entries per hour. Hence the code change to log machine name and a guid generation to guarantee uniqueness.

I need this urgently so I am going to use this modified version regardless of pull request agreement. However, I would really appreciate it if you can consider accepting the pull request.