feat(core): properly support inheritance

## Inheritance Semantics:

Decorators:
1) list the decorators of the class and its parents in the ancestor first order
2) only use the last decorator of each kind (e.g. @Component / ...)

Constructor parameters:
If a class inherits from a parent class and does not declare
a constructor, it inherits the parent class constructor,
and with it the parameter metadata of that parent class.

Lifecycle hooks:
Follow the normal class inheritance model,
i.e. lifecycle hooks of parent classes will be called
even if the method is not overwritten in the child class.

## Example

E.g. the following is a valid use of inheritance and it will
also inherit all metadata:

```
@Directive({selector: 'someDir'})
class ParentDirective {
  constructor(someDep: SomeDep) {}

  ngOnInit() {}
}

class ChildDirective extends ParentDirective {}
```

Closes #11606
Closes #12892

modules/@angular/compiler/test/pipe_resolver_spec.ts

@@ -0,0 +1,52 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {PipeResolver} from '@angular/compiler/src/pipe_resolver';
+import {Pipe} from '@angular/core/src/metadata';
+import {stringify} from '../src/facade/lang';
+
+@Pipe({name: 'somePipe', pure: true})
+class SomePipe {
+}
+
+class SimpleClass {}
+
+export function main() {
+  describe('PipeResolver', () => {
+    let resolver: PipeResolver;
+
+    beforeEach(() => { resolver = new PipeResolver(); });
+
+    it('should read out the metadata from the class', () => {
+      const moduleMetadata = resolver.resolve(SomePipe);
+      expect(moduleMetadata).toEqual(new Pipe({name: 'somePipe', pure: true}));
+    });
+
+    it('should throw when simple class has no pipe decorator', () => {
+      expect(() => resolver.resolve(SimpleClass))
+          .toThrowError(`No Pipe decorator found on ${stringify(SimpleClass)}`);
+    });
+
+    it('should support inheriting the metadata', function() {
+      @Pipe({name: 'p'})
+      class Parent {
+      }
+
+      class ChildNoDecorator extends Parent {}
+
+      @Pipe({name: 'c'})
+      class ChildWithDecorator extends Parent {
+      }
+
+      expect(resolver.resolve(ChildNoDecorator)).toEqual(new Pipe({name: 'p'}));
+
+      expect(resolver.resolve(ChildWithDecorator)).toEqual(new Pipe({name: 'c'}));
+    });
+
+  });
+}