fix(errors): [2/2] Rename Exception to Error; remove from public API

BREAKING CHANGE:

Exceptions are no longer part of the public API. We don't expect that anyone should be referring to the Exception types.

ExceptionHandler.call(exception: any, stackTrace?: any, reason?: string): void;
change to:
ErrorHandler.handleError(error: any): void;

modules/@angular/core/testing/test_compiler.ts

@@ -7,7 +7,7 @@
  */
 
 import {Compiler, CompilerOptions, ComponentMetadataType, DirectiveMetadataType, Injector, NgModuleMetadataType, PipeMetadataType} from '../index';
-import {unimplemented} from '../src/facade/exceptions';
+import {unimplemented} from '../src/facade/errors';
 import {Type} from '../src/type';
 import {MetadataOverride} from './metadata_override';