Phoenix 180 1

A new pull request with updated comments.  Still trying to test the performance with these changes.
-> Test cases are not running and all the test cases are failing at the deleteTable sequence.
-> The checking of the timestamp stored in the table and avoiding concurrent update stats does not work. I am checking on it.
-> The clearing of the metadata cache should happen in a lock? If so then we need to see every where (even while reading from the cache) we should introduce a new lock.
-> Estimated byte size() is yet to be added to Ptable
-> Multi CF is not yet tested.  
But this would help in getting the review done on the latest changes.