Better docs of CorDapp structure and node interaction (#3761)

* Clean-up. Instructions on how template would be modified for production.

* Change page titles to make it clearer make they contain.

* Simple example of how to connect to node via RPC. Explanation of how to interact with node via RPC.

* Bigger warning about deprecated webserver. Makes it clear that CordaRPCClient is THE way to interact with a node.

* Review from Clinton.

* Separating template info from general info.

docs/source/example-code/src/main/java/net/corda/docs/ClientRpcExampleJava.java

@@ -0,0 +1,34 @@
+package net.corda.docs;
+
+// START 1
+import net.corda.client.rpc.CordaRPCClient;
+import net.corda.client.rpc.CordaRPCConnection;
+import net.corda.core.messaging.CordaRPCOps;
+import net.corda.core.utilities.NetworkHostAndPort;
+import org.apache.activemq.artemis.api.core.ActiveMQException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.ExecutionException;
+
+class ExampleRpcClientJava {
+    private static final Logger logger = LoggerFactory.getLogger(ExampleRpcClient.class);
+
+    public static void main(String[] args) throws ActiveMQException, InterruptedException, ExecutionException {
+        if (args.length != 3) {
+            throw new IllegalArgumentException("Usage: TemplateClient <node address> <username> <password>");
+        }
+        final NetworkHostAndPort nodeAddress = NetworkHostAndPort.parse(args[0]);
+        String username = args[1];
+        String password = args[2];
+
+        final CordaRPCClient client = new CordaRPCClient(nodeAddress);
+        final CordaRPCConnection connection = client.start(username, password);
+        final CordaRPCOps cordaRPCOperations = connection.getProxy();
+
+        logger.info(cordaRPCOperations.currentNodeTime().toString());
+
+        connection.notifyServerAndClose();
+    }
+}
+// END 1

docs/source/example-code/src/main/kotlin/net/corda/docs/ClientRpcExample.kt

@@ -0,0 +1,31 @@
+@file:Suppress("unused")
+
+package net.corda.docs
+
+// START 1
+import net.corda.client.rpc.CordaRPCClient
+import net.corda.core.utilities.NetworkHostAndPort.Companion.parse
+import net.corda.core.utilities.loggerFor
+import org.slf4j.Logger
+
+class ExampleRpcClient {
+    companion object {
+        val logger: Logger = loggerFor<ExampleRpcClient>()
+    }
+
+    fun main(args: Array<String>) {
+        require(args.size == 3) { "Usage: TemplateClient <node address> <username> <password>" }
+        val nodeAddress = parse(args[0])
+        val username = args[1]
+        val password = args[2]
+
+        val client = CordaRPCClient(nodeAddress)
+        val connection = client.start(username, password)
+        val cordaRPCOperations = connection.proxy
+
+        logger.info(cordaRPCOperations.currentNodeTime().toString())
+
+        connection.notifyServerAndClose()
+    }
+}
+// END 1