[LYN-2470] Integrate resource mapping tool with engine python environment (#17)

1. Add support to use engine python runtime environment. Ideally we should use project executable directory which contains required qt binaries after build. But currently Qt plugins are not put under proper subdirectory which causes huge overhead of loading plugin binaries (see details in this jira https://jira.agscollab.com/browse/LYN-2669 ). The temporary solution is to use AWSCore.Editor target to create a subdirectory for our use case.   
2. **Minor Fix** After migrating to engine python environment, see boto3 warning while using debug mode, seems like a existing issue for a long time https://github.com/boto/boto3/issues/454. Register a after call event to close connection   
3. **Minor Fix** After migrating to engine python environment, see Qt multithread warning while using debug mode, change direct setter function call to qt signal

Gems/AWSCore/Code/Tools/ResourceMappingTool/manager/controller_manager.py

@@ -51,4 +51,5 @@ class ControllerManager(object):
         logger.info("Setting up ViewEdit and ImportResource controllers ...")
         self._view_edit_controller.setup()
         self._import_resources_controller.setup()
-        self._import_resources_controller.add_import_resources.connect(self._view_edit_controller.add_import_resources)
+        self._import_resources_controller.add_import_resources_sender.connect(
+            self._view_edit_controller.add_import_resources_receiver)