Upgrade to latest version of @graknlabs_protocol (#53)

## What is the goal of this PR?

Adapt to latest changes in Python generated code of Grakn Protocol

## What are the changes implemented in this PR?

- Change code to import generated code from `grakn_protocol`
- Upgrade `@graknlabs_build_tools`

Author: vmax

dependencies/graknlabs/dependencies.bzl

@@ -22,7 +22,7 @@ def graknlabs_build_tools():
     git_repository(
         name = "graknlabs_build_tools",
         remote = "https://github.com/graknlabs/build-tools",
-        commit = "27a4596b4338189e9529cff3d015f173e6eb4c5b", # sync-marker: do not remove this comment, this is used for sync-dependencies by @graknlabs_build_tools
+        commit = "e1875797063b86386072034e65af2f40dc1fb07c", # sync-marker: do not remove this comment, this is used for sync-dependencies by @graknlabs_build_tools
     )
 
 def graknlabs_grakn_core():

grakn/client.py

@@ -6,7 +6,7 @@
 from grakn.service.Session.util.enums import TxType as _TxType
 from grakn.service.Keyspace.KeyspaceService import KeyspaceService
 from grakn.service.Session.TransactionService import TransactionService
-from session.Session_pb2_grpc import SessionServiceStub
+from grakn_protocol.session.Session_pb2_grpc import SessionServiceStub
 from grakn.exception.GraknError import GraknError
 
 class GraknClient(object):

grakn/service/Keyspace/KeyspaceService.py

@@ -17,8 +17,8 @@
 # under the License.
 #
 
-from keyspace.Keyspace_pb2_grpc import KeyspaceServiceStub
-import keyspace.Keyspace_pb2 as keyspace_messages
+from grakn_protocol.keyspace.Keyspace_pb2_grpc import KeyspaceServiceStub
+import grakn_protocol.keyspace.Keyspace_pb2 as keyspace_messages
 
 class KeyspaceService(object):
 

grakn/service/Session/Concept/BaseTypeMapping.py

@@ -17,7 +17,7 @@
 # under the License.
 #
 
-import session.Concept_pb2 as ConceptMessages
+import grakn_protocol.session.Concept_pb2 as ConceptMessages
 
 
 # base type constant names 

grakn/service/Session/util/RequestBuilder.py

@@ -18,8 +18,8 @@
 #
 from datetime import datetime
 
-import session.Session_pb2 as transaction_messages
-import session.Concept_pb2 as concept_messages
+import grakn_protocol.session.Session_pb2 as transaction_messages
+import grakn_protocol.session.Concept_pb2 as concept_messages
 from grakn.service.Session.util import enums
 from grakn.service.Session.Concept import BaseTypeMapping
 

grakn/service/Session/util/enums.py

@@ -18,8 +18,8 @@
 #
 
 from enum import Enum
-import session.Session_pb2 as SessionMessages
-import session.Concept_pb2 as ConceptMessages
+import grakn_protocol.session.Session_pb2 as SessionMessages
+import grakn_protocol.session.Concept_pb2 as ConceptMessages
 
 
 class TxType(Enum):