Introducing caching

Fix #832 #752

Adds caching capabilities to the converter. Remote calls to the
registry, Schema Parsing and toString were very expensive operations
that are now being cached

Adds a decorator to the registryClient that allows caching of remote
invocations.

Fixing review comments

spring-cloud-stream-schema/pom.xml

@@ -8,7 +8,9 @@
 	<modelVersion>4.0.0</modelVersion>
 
 	<artifactId>spring-cloud-stream-schema</artifactId>
-
+	<properties>
+		<avro.version>1.8.1</avro.version>
+	</properties>
 
 	<dependencies>
 		<dependency>
@@ -28,7 +30,7 @@
 		<dependency>
 			<groupId>org.apache.avro</groupId>
 			<artifactId>avro</artifactId>
-			<version>1.8.1</version>
+			<version>${avro.version}</version>
 			<optional>true</optional>
 		</dependency>
 		<dependency>
@@ -47,4 +49,26 @@
 			<scope>test</scope>
 		</dependency>
 	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.avro</groupId>
+				<artifactId>avro-maven-plugin</artifactId>
+				<version>${avro.version}</version>
+				<executions>
+					<execution>
+						<phase>generate-test-sources</phase>
+						<goals>
+							<goal>schema</goal>
+						</goals>
+
+					</execution>
+				</executions>
+				<configuration>
+					<testOutputDirectory>${project.basedir}/target/generated-test-sources</testOutputDirectory>
+					<testSourceDirectory>${project.basedir}/src/test/resources/schemas</testSourceDirectory>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
 </project>