Launcher can now load servers in addition to regular applications.

* Add new ServerMain interface
* AppProvider can now choose to load ServerMain or AppMain classes
* Explicitly document what happens if something doesn't match an
  expected interface
* Improve error message on inability to load something.
* Parse new [server] section that denotes a service and is lock file
* Ability to serialize launch configurations.
* Attempt to look for active listening server via the lock file
* Forks the launcher itself to run servers from serialized launch configuration.
* Testing echo server.
* Tests to detect basic server functionality will work.
* Revamp all the documentation for the launcher, giving it its own section.
* Full documentation on launcher configuration files.

Revamp launcher documentation to be a bit more in-depth, and split bits into sections.

launch/interface/src/main/java/xsbti/AppMain.java

@@ -1,6 +1,25 @@
 package xsbti;
 
+/**
+ * The main entry interface for launching applications.   Classes which implement this interface
+ * can be launched via the sbt launcher.
+ * 
+ * In addition, classes can be adapted into this interface by the launcher if they have a static method
+ * matching one of these signatures:
+ * 
+ * - public static void main(String[] args)
+ * - public static int main(String[] args)
+ * - public static xsbti.Exit main(String[] args)
+ *
+ */
 public interface AppMain
 {
+	/** Run the application and return the result.
+	 * 
+	 * @param configuration  The configuration used to run the application.  Includes arguments and access to launcher features.
+	 * @return
+	 *        The result of running this app.  
+	 *        Note: the result can be things like "Please reboot this application". 
+	 */
 	public MainResult run(AppConfiguration configuration);
 }

launch/interface/src/main/java/xsbti/AppProvider.java

@@ -3,9 +3,10 @@ package xsbti;
 import java.io.File;
 
 /**
- * This represents an interface that can generate applications.
+ * This represents an interface that can generate applications or servers.
  * 
- *  An application is somethign which will run and return an exit value.
+ * This provider grants access to launcher related features associated with
+ * the id.
  */
 public interface AppProvider
 {
@@ -33,6 +34,8 @@ public interface AppProvider
 	* It is NOT guaranteed that newMain().getClass() == mainClass().
 	* The sbt launcher can wrap generic static main methods. In this case, there will be a wrapper class,
 	* and you must use the `entryPoint` method.
+	* @throws IncompatibleClassChangeError if the configuration used for this Application does not
+	*                                         represent a launched application.
 	*/
 	public AppMain newMain();
 	

launch/interface/src/main/java/xsbti/Server.java

@@ -0,0 +1,36 @@
+package xsbti;
+
+/** A running server.
+ * 
+ * A class implementing this must:
+ * 
+ * 1. Expose an HTTP port that clients can connect to, returned via the uri method.
+ * 2. Accept HTTP HEAD requests against the returned URI. These are used as "ping" messages to ensure
+ *    a server is still alive, when new clients connect.
+ * 3. Create a new thread to execute its service
+ * 4. Block the calling thread until the server is shutdown via awaitTermination()
+ */
+public interface Server {
+	/**
+	 * @return
+	 *    A URI denoting the Port which clients can connect to.  
+	 *
+	 *    Note: we use a URI so that the server can bind to different IP addresses (even a public one) if desired.
+	 *    Note: To verify that a server is "up", the sbt launcher will attempt to connect to
+	 *          this URI's address and port with a socket.  If the connection is accepted, the server is assumed to
+	 *          be working.
+	 */
+	public java.net.URI uri();
+	/**
+	 * This should block the calling thread until the server is shutdown.
+     * 
+	 * @return
+	 *      The result that should occur from the server.
+	 *      Can be:
+	 *      - xsbti.Exit:  Shutdown this launch
+	 *      - xsbti.Reboot:  Restart the server
+	 *      
+	 *
+	 */
+	public xsbti.MainResult awaitTermination();
+}

launch/interface/src/main/java/xsbti/ServerMain.java

@@ -0,0 +1,17 @@
+package xsbti;
+
+/** The main entry point for a launched service.  This allows applciations
+ * to instantiate server instances.
+ */
+public interface ServerMain {
+  /**
+   * This method should launch one or more thread(s) which run the service.  After the service has
+   * been started, it should return the port/URI it is listening for connections on.
+   * 
+   * @param configuration
+   *          The configuration used to launch this service.
+   * @return
+   *    A running server.
+   */
+  public Server start(AppConfiguration configuration);
+}