Added a sample that illustrates using multiple DataSources

This PR adds a sample that illustrates the use of multiple DataSources
in a single Spring Cloud Task application.

Resolves #413

Updated based on code review

spring-cloud-task-samples/multiple-datasources/src/test/resources/application.properties

@@ -0,0 +1,18 @@
+#
+# Copyright 2016 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+spring.application.name=Demo Multiple DataSources Task
+logging.level.org.springframework.cloud.task=DEBUG