Remove the need to extend JFrame in ClientUI

- Make ClientUI wrap JFrame inside
- Do not make RuneLite class depend on Swing API at all
- Create ClientUI through Guice
- Simplify initialization and showing of UI

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

runelite-client/src/test/java/net/runelite/client/plugins/PluginManagerTest.java

@@ -45,7 +45,6 @@ import joptsimple.OptionSet;
 import net.runelite.api.Client;
 import net.runelite.client.RuneLite;
 import net.runelite.client.RuneLiteModule;
-import net.runelite.client.ui.ClientUI;
 import static org.junit.Assert.assertEquals;
 import org.junit.Before;
 import org.junit.Rule;
@@ -67,9 +66,6 @@ public class PluginManagerTest
 	private RuneLite runelite;
 	private Set<Class> pluginClasses;
 
-	@Mock
-	ClientUI clientUi;
-
 	@Mock
 	Client client;
 
@@ -83,7 +79,6 @@ public class PluginManagerTest
 		RuneLite.setInjector(injector);
 
 		runelite = injector.getInstance(RuneLite.class);
-		runelite.setGui(clientUi);
 
 		// Find plugins we expect to have
 		pluginClasses = new HashSet<>();