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/NetworkConnection.h

@@ -18,12 +18,13 @@
 #include "ntcore_cpp.h"
 
 namespace wpi {
+class Logger;
 class NetworkStream;
 }
 
 namespace nt {
 
-class Notifier;
+class IConnectionNotifier;
 
 class NetworkConnection {
  public:
@@ -40,8 +41,10 @@ class NetworkConnection {
   typedef std::vector<std::shared_ptr<Message>> Outgoing;
   typedef wpi::ConcurrentQueue<Outgoing> OutgoingQueue;
 
-  NetworkConnection(std::unique_ptr<wpi::NetworkStream> stream,
-                    Notifier& notifier, HandshakeFunc handshake,
+  NetworkConnection(unsigned int uid,
+                    std::unique_ptr<wpi::NetworkStream> stream,
+                    IConnectionNotifier& notifier, wpi::Logger& logger,
+                    HandshakeFunc handshake,
                     Message::GetEntryTypeFunc get_entry_type);
   ~NetworkConnection();
 
@@ -60,7 +63,6 @@ class NetworkConnection {
 
   void QueueOutgoing(std::shared_ptr<Message> msg);
   void PostOutgoing(bool keep_alive);
-  void NotifyIfActive(ConnectionListenerCallback callback) const;
 
   unsigned int uid() const { return m_uid; }
 
@@ -82,11 +84,10 @@ class NetworkConnection {
   void ReadThreadMain();
   void WriteThreadMain();
 
-  static std::atomic_uint s_uid;
-
   unsigned int m_uid;
   std::unique_ptr<wpi::NetworkStream> m_stream;
-  Notifier& m_notifier;
+  IConnectionNotifier& m_notifier;
+  wpi::Logger& m_logger;
   OutgoingQueue m_outgoing;
   HandshakeFunc m_handshake;
   Message::GetEntryTypeFunc m_get_entry_type;