Favor use of Properties vs. for configuration

This reverts a number of changes made in commit 3033a19. Primary changes
include:

 - Restoring the immutability of the Node class

 - The argparse4j Namespace object is no longer passed down through
   Guice modules

 - Instead, arguments are eagerly read from the Namespace object by the
   #main method and these values are used to populate the Properties
   object that is already supplied to each Guice module

Other changes include:

 - The addition of a BootstrapNodes#DEFAULT_BOOTSTRAP_NODE field as
   a convenient alias to BootstrapNodes#DIGITAL_OCEAN_1 (or whatever the
   future default bootstrap node may be)

 - A Node#getPortAsString method has been added for convenience when
   dealing with String-based properties

 - A variant of the Node#at static factory method has been added which
   accepts the port value as a String vs. an int--again this is for
   convenience when dealing with String-based properties

 - Tests have been added to NodeTests to reflect the above

src/test/java/io/bitsquare/app/gui/ViewLoaderTests.java

@@ -25,6 +25,7 @@ import com.google.inject.Guice;
 import com.google.inject.Injector;
 
 import java.util.HashMap;
+import java.util.Properties;
 
 import javafx.application.Application;
 import javafx.stage.Stage;
@@ -63,9 +64,7 @@ public class ViewLoaderTests {
 
     @Before
     public void setUp() {
-        Injector injector = Guice.createInjector(new MainModule("testApp",
-                new Namespace(new HashMap<>()),
-                TestApp.primaryStage));
+        Injector injector = Guice.createInjector(new MainModule(new Properties(), "testApp", TestApp.primaryStage));
         ViewLoader.setInjector(injector);
     }
 

src/test/java/io/bitsquare/network/NodeTests.java

@@ -44,6 +44,14 @@ public class NodeTests {
         Node node2 = Node.at("bitsquare2.example.com", "203.0.113.2");
         assertThat(node1a.hashCode(), equalTo(node1b.hashCode()));
         assertThat(node1a.hashCode(), not(equalTo(node2.hashCode())));
+
+        assertThat(node1a.getPort(), equalTo(Node.DEFAULT_PORT));
+        assertThat(node1a.getPortAsString(), equalTo(String.valueOf(Node.DEFAULT_PORT)));
+
+        Node node3a = Node.at("bitsquare3.example.com", "203.0.113.3", 1234);
+        Node node3b = Node.at("bitsquare3.example.com", "203.0.113.3", "1234");
+
+        assertThat(node3a, equalTo(node3b));
     }
 
     @Test