Adding initial interface for backend and redis pubsub (#19)

* Adding initial interface for backend and redis pubsub

* Addressing comments, adding super in all memories

* Removing distributed experience replay

rl_coach/memories/backend/memory_impl.py

@@ -0,0 +1,21 @@
+
+from rl_coach.memories.backend.memory import MemoryBackendParameters
+from rl_coach.memories.backend.redis import RedisPubSubBackend, RedisPubSubMemoryBackendParameters
+
+
+def get_memory_backend(params: MemoryBackendParameters):
+
+    backend = None
+    if type(params) == RedisPubSubMemoryBackendParameters:
+        backend = RedisPubSubBackend(params)
+
+    return backend
+
+
+def construct_memory_params(json: dict):
+
+    if json['store_type'] == 'redispubsub':
+        memory_params = RedisPubSubMemoryBackendParameters(
+            json['redis_address'], json['redis_port'], channel=json.get('channel', ''), run_type=json['run_type']
+        )
+        return memory_params