Implement independent instances.

Previously, most of the classes were implemented as singletons so only one
instance was possible.

This change adds an instance handle-based API.  In Java, this API is located
in a different package than the old API (edu.wpi.first.networktables).

Backwards compatibility with ITable and the old NetworkTable API is largely
maintained, but a handful of classes have moved to the new package in Java
(ConnectionInfo and PersistentException), and the old JNI has been completed
replaced.

Also:
- Move SetTeam implementation to Dispatcher.
- Consistently pass time through Java and C++ Value API.
- Rename nt_Value.h to NetworkTableValue.h for consistency with Java.
- Improve documentation
- Make C++ and Java APIs more consistent
- Document RPC functions and support RPC in Java.
- Add polling features for entry and connection listeners and use them to
  move callback threads to Java level.
- Remove thread start and stop hooks (as polling is available).
- Make Notifiers, RpcServer, Dispatcher, and Storage mockable.
- Set NOTIFY_NEW on immediate entry notifications.
- Make GetTable("/") and GetTable("") equivalent.
- Generate local notification for flags update when loading persistent file.

And many unit test updates/changes:
- Use InitGoogleMock instead of InitGoogleTest in test main.
- Move test printers to TestPrinter.h/cpp.
- Provide printers for StringRef, EntryNotifier, and Handle.
- StorageTest: Check notifications.
- Add entry notifier unit tests.
- Storage: Add test for incoming entry assignment.
- Update connection listener tests.
- Add entry listener unit tests.

Fixes #11, #140, #189, #190, #192, #193, #221

src/main/native/cpp/InstanceImpl.h

@@ -0,0 +1,60 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2016-2017. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef NT_INSTANCEIMPL_H_
+#define NT_INSTANCEIMPL_H_
+
+#include <atomic>
+#include <memory>
+#include <mutex>
+
+#include "support/UidVector.h"
+
+#include "ConnectionNotifier.h"
+#include "Dispatcher.h"
+#include "DsClient.h"
+#include "EntryNotifier.h"
+#include "Log.h"
+#include "LoggerImpl.h"
+#include "RpcServer.h"
+#include "Storage.h"
+
+namespace nt {
+
+class InstanceImpl {
+ public:
+  explicit InstanceImpl(int inst);
+  ~InstanceImpl();
+
+  // Instance repository
+  static InstanceImpl* GetDefault();
+  static InstanceImpl* Get(int inst);
+  static int GetDefaultIndex();
+  static int Alloc();
+  static void Destroy(int inst);
+
+  LoggerImpl logger_impl;
+  wpi::Logger logger;
+  ConnectionNotifier connection_notifier;
+  EntryNotifier entry_notifier;
+  RpcServer rpc_server;
+  Storage storage;
+  Dispatcher dispatcher;
+  DsClient ds_client;
+
+ private:
+  static int AllocImpl();
+
+  static std::atomic<int> s_default;
+  static std::atomic<InstanceImpl*> s_fast_instances[10];
+  static wpi::UidVector<std::unique_ptr<InstanceImpl>, 10> s_instances;
+  static std::mutex s_mutex;
+};
+
+}  // namespace nt
+
+#endif  // NT_INSTANCEIMPL_H_