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/java/edu/wpi/first/networktables/LogMessage.java

@@ -0,0 +1,75 @@
+/*----------------------------------------------------------------------------*/
+/* 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.networktables;
+
+/**
+ * NetworkTables log message.
+ */
+public final class LogMessage {
+  /**
+   * Logging levels.
+   */
+  public static final int kCritical = 50;
+  public static final int kError = 40;
+  public static final int kWarning = 30;
+  public static final int kInfo = 20;
+  public static final int kDebug = 10;
+  public static final int kDebug1 = 9;
+  public static final int kDebug2 = 8;
+  public static final int kDebug3 = 7;
+  public static final int kDebug4 = 6;
+
+  /**
+   * The logger that generated the message.
+   */
+  public final int logger;
+
+  /**
+   * Log level of the message.
+   */
+  public final int level;
+
+  /**
+   * The filename of the source file that generated the message.
+   */
+  public final String filename;
+
+  /**
+   * The line number in the source file that generated the message.
+   */
+  public final int line;
+
+  /**
+   * The message.
+   */
+  public final String message;
+
+  /** Constructor.
+   * This should generally only be used internally to NetworkTables.
+   * @param inst Instance
+   * @param logger Logger
+   * @param level Log level
+   * @param filename Filename
+   * @param line Line number
+   * @param message Message
+   */
+  public LogMessage(NetworkTableInstance inst, int logger, int level, String filename, int line, String message) {
+    this.inst = inst;
+    this.logger = logger;
+    this.level = level;
+    this.filename = filename;
+    this.line = line;
+    this.message = message;
+  }
+
+  private final NetworkTableInstance inst;
+
+  NetworkTableInstance getInstance() {
+    return inst;
+  }
+}