Pull args, intl, logging, shelf, and source_maps out of the SDK.

pkg/logging/README.md

-## Initializing
-
-By default, the logging package does not do anything useful with the
-log messages. You must configure the logging level and add a handler
-for the log messages.
-
-Here is a simple logging configuration that logs all messages
-via `print`.
-
-```dart
-Logger.root.level = Level.ALL;
-Logger.root.onRecord.listen((LogRecord rec) {
-  print('${rec.level.name}: ${rec.time}: ${rec.message}');
-});
-```
-
-First, set the root [Level]. All messages at or above the level are
-sent to the [onRecord] stream.
-
-Then, listen on the [onRecord] stream for [LogRecord] events. The
-[LogRecord] class has various properties for the message, error,
-logger name, and more.
-
-## Logging messages
-
-Create a [Logger] with a unique name to easily identify the source
-of the log messages.
-
-```dart
-final Logger log = new Logger('MyClassName');
-```
-
-Here is an example of logging a debug message and an error:
-
-```dart
-var future = doSomethingAsync().then((result) {
-  log.fine('Got the result: $result');
-  processResult(result);
-}).catchError((e, stackTrace) => log.severe('Oh noes!', e, stackTrace));
-```
-
-When logging more complex messages, you can pass a closure instead
-that will be evaluated only if the message is actually logged:
-
-```dart
-  log.fine(() => [1, 2, 3, 4, 5].map((e) => e * 4).join("-"));
-```
-
-See the [Logger] class for the different logging methods.