General attribute-based heterogeneity support with hard and soft constraints (#248)

* attribute-based heterogeneity-awareness in global scheduler and photon

* minor post-rebase fix

* photon: enforce dynamic capacity constraint on task dispatch

* globalsched: cap the number of times we try to schedule a task in round robin

* propagating ability to specify resource capacity to ray.init

* adding resources to remote function export and fetch/register

* globalsched: remove unused functions; update cached photon resource capacity (until next photon heartbeat)

* Add some integration tests.

* globalsched: cleanup + factor out constraint checking

* lots of style

* task_spec_required_resource: global refactor

* clang format

* clang format + comment update in photon

* clang format photon comment

* valgrind

* reduce verbosity for Travis

* Add test for scheduler load balancing.

* addressing comments

* refactoring global scheduler algorithm

* Minor cleanups.

* Linting.

* Fix array_test.py and linting.

* valgrind fix for photon tests

* Attempt to fix stress tests.

* fix hashmap free

* fix hashmap free comment

* memset photon resource vectors to 0 in case they get used before the first heartbeat

* More whitespace changes.

* Undo whitespace error I introduced.

python/plasma/plasma.py

@@ -100,6 +100,8 @@ class PlasmaClient(object):
       store_socket_name (str): Name of the socket the plasma store is listening at.
       manager_socket_name (str): Name of the socket the plasma manager is listening at.
     """
+    self.store_socket_name = store_socket_name
+    self.manager_socket_name = manager_socket_name
     self.alive = True
 
     if manager_socket_name is not None: