Implement device-to-computer clipboard copy

On Ctrl+C:
 - the client sends a GET_CLIPBOARD command to the device;
 - the device retrieve its current clipboard text and sends it in a
   GET_CLIPBOARD device event;
 - the client sets this text as the system clipboard text, so that it
   can be pasted in another application.

Fixes <https://github.com/Genymobile/scrcpy/issues/145>

server/src/main/java/com/genymobile/scrcpy/wrappers/ServiceManager.java

@@ -15,6 +15,7 @@ public final class ServiceManager {
     private InputManager inputManager;
     private PowerManager powerManager;
     private StatusBarManager statusBarManager;
+    private ClipboardManager clipboardManager;
 
     public ServiceManager() {
         try {
@@ -68,4 +69,11 @@ public final class ServiceManager {
         }
         return statusBarManager;
     }
+
+    public ClipboardManager getClipboardManager() {
+        if (clipboardManager == null) {
+            clipboardManager = new ClipboardManager(getService("clipboard", "android.content.IClipboard"));
+        }
+        return clipboardManager;
+    }
 }