* factoring out object_info for general use by several Ray components
* addressing comments
* Replace SHA256 task hash with MD5
Add object hash to object table (always overwrites)
Support for table operations that span multiple asynchronous Redis
commands
Add a new object location in a transaction, using Redis's optimistic
concurrency
Use Redis GETSET instead of transactions and Python frontend code for object hashing
Remove spurious log message
Fix for object_table_add
Revert "Replace SHA256 task hash with MD5"
This reverts commit e599de473c8dad9189ccb0600429534b469b76a2.
Revert to sha256
Test case for illegal puts
Use SETNX to set object hashes
Initialize digest with zeros
Initialize plasma_request with zeros
* Fixes
* replace SHA256 with a faster hash in the object store
* Fix valgrind
* Address Robert's comments
* Check that plasma_compute_object_hash succeeds.
* Don't run test_illegal_put test with valgrind because it causes an intentional crash which causes valgrind to complain.
* Debugging after rebase.
* handling Robert's comments
* Fix bugs after rebase.
* final fixes for Stephanie's PR
* fix
