feat(dart/transform): Add debug transform parameters

Add two transform parameters to aid in debugging the transformer
- `mirror_mode`, with values {`debug`, `none`, and `verbose`}
- `init_reflector`, with values {`true`, `false`}

`mirror_mode`:
- `debug`: Allow reflective access, but log a message if it is used
- `none`: Remove reflective access, `throw` if it is used. Default value
- `verbose`: Allow reflective access, log a stack trace if it is used

`init_reflector`: Whether to generate calls to our generated
`initReflector` code.

These will be useful to reveal areas where the transformer is not generating
appropriate code and to quickly see where reflective accesses occur.

When the pub mode is `transform_dynamic`, we run in MirrorMode.debug
with `init_reflector = false`. This is used for testing purposes.

modules/angular2/test/transform/reflection_remover/debug_files/README.md

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+Tests that the reflection removal step:
+ 1. Comments out the import of reflection_capabilities.dart
+ 2. Comments out the instantiation of `ReflectionCapabilities`
+ 3. Adds the appropriate import.
+ 4. Adds the call to `initReflector`
+ 5. Does not change line numbers in the source.
+ 6. Makes minimal changes to source offsets.

modules/angular2/test/transform/reflection_remover/debug_files/expected/index.dart

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+library angular2.test.transform.debug_reflection_remover_files;
+
+// This file is intentionally formatted as a string to avoid having the
+// automatic transformer prettify it.
+//
+// This file represents transformed user code. Because this code will be
+// linked to output by a source map, we cannot change line numbers from the
+// original code and we therefore add our generated code on the same line as
+// those we are removing.
+
+var code = """
+library web_foo;
+
+import 'package:angular2/src/core/application.dart';
+import 'package:angular2/src/reflection/reflection.dart';
+import 'package:angular2/src/reflection/debug_reflection_capabilities.dart';import 'index.ng_deps.dart' as ngStaticInit0;
+
+void main() {
+  reflector.reflectionCapabilities = new ReflectionCapabilities();ngStaticInit0.initReflector(reflector);
+  bootstrap(MyComponent);
+}
+""";

modules/angular2/test/transform/reflection_remover/debug_files/index.dart

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+library web_foo;
+
+import 'package:angular2/src/core/application.dart';
+import 'package:angular2/src/reflection/reflection.dart';
+import 'package:angular2/src/reflection/reflection_capabilities.dart';
+
+void main() {
+  reflector.reflectionCapabilities = new ReflectionCapabilities();
+  bootstrap(MyComponent);
+}