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/test/native/cpp/TestPrinters.h

@@ -0,0 +1,54 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 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_TEST_TESTPRINTERS_H_
+#define NT_TEST_TESTPRINTERS_H_
+
+#include <memory>
+#include <ostream>
+
+#include "gtest/gtest.h"
+
+#include "llvm/StringRef.h"
+
+namespace llvm {
+
+inline void PrintTo(StringRef str, ::std::ostream *os) {
+  ::testing::internal::PrintStringTo(str.str(), os);
+}
+
+}  // namespace llvm
+
+namespace nt {
+
+class EntryNotification;
+class Handle;
+class Message;
+class Value;
+
+void PrintTo(const EntryNotification& event, std::ostream* os);
+void PrintTo(const Handle& handle, std::ostream* os);
+
+void PrintTo(const Message& msg, std::ostream* os);
+
+inline void PrintTo(std::shared_ptr<Message> msg, std::ostream* os) {
+  *os << "shared_ptr{";
+  if (msg) PrintTo(*msg, os);
+  *os << '}';
+}
+
+void PrintTo(const Value& value, std::ostream* os);
+
+inline void PrintTo(std::shared_ptr<Value> value, std::ostream* os) {
+  *os << "shared_ptr{";
+  if (value) PrintTo(*value, os);
+  *os << '}';
+}
+
+}  // namespace nt
+
+#endif  // NT_TEST_TESTPRINTERS_H_