Add client starter module

This adds a starter module that includes the Spring gRPC
core module and the grpc-stub dependency.

Also, makes the `grpc-stub` dependency optional in Spring
gRPC core module.

Signed-off-by: Chris Bono <chris.bono@gmail.com>

spring-grpc-client-spring-boot-starter/pom.xml

@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.grpc</groupId>
+		<artifactId>spring-grpc</artifactId>
+		<version>0.4.0-SNAPSHOT</version>
+	</parent>
+	<artifactId>spring-grpc-client-spring-boot-starter</artifactId>
+	<packaging>jar</packaging>
+	<name>Spring gRPC Client Spring Boot Starter</name>
+	<description>Spring gRPC Client Spring Boot Starter</description>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.grpc</groupId>
+			<artifactId>spring-grpc-core</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.grpc</groupId>
+			<artifactId>spring-grpc-spring-boot-autoconfigure</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-netty</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-stub</artifactId>
+        </dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter</artifactId>
+			<version>${spring-boot.version}</version>
+		</dependency>
+	</dependencies>
+
+</project>