Java demos use package metadata directive (#24)

[rysamurai]

The Java demos in the ice-demos repository now demonstrate the package metadata directive.
"Ice.Default.Package" property is set after the communicator is created, as opposed to being set in the config files.

[bernardnormier]

The package metadata is missing for some demos: Chat, Database and android.

[rysamurai]

Thanks for letting me know, I'll get to work on adding it right away.

[bernardnormier]

The updated Chat and Manual/simpleFilesystem don't compile, most likely because of a clean issue (./gradlew clean apparently didn't clean old generated code).

Then, a few demos already used packages:

Manual/evictor/EvictorBase.java:package Evictor;
Manual/evictor/LinkedList.java:package Evictor;
Manual/lifecycle/FilesystemI/DirectoryI.java:package FilesystemI;
Manual/lifecycle/FilesystemI/FileI.java:package FilesystemI;
Manual/lifecycle/FilesystemI/NodeI.java:package FilesystemI;
Chat/src/main/java/ChatDemoGUI/ChatRoomCallbackI.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/ChatDemoGUIFactory.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/StatusBarI.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/Coordinator.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/LoginView.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/ChatView.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/ChatUtils.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/LoginInfo.java:package ChatDemoGUI;
Chat/src/main/java/ChatDemoGUI/MainView.java:package ChatDemoGUI;

For the Manual demos, I think we should move these classes to the top-level package, just like Client and Server. And of course update the Ice Manual.

For the Chat demo, I would move this code from package ChatDemoGUI to package com.zeroc.demos.Chat (like the generated code for that demo).