feat(input): add (limited) support for text masking

#### Bug, feature request, or proposal:
How can I set a text mask in date picker component so, if user doesn't want to select a date in calendar, he can type and fill correctly the field?

#### What is the expected behavior?
When click on input date picker, show the mask so user can type date instead of selecting a date from calendar

#### What is the current behavior?
empty input

#### What are the steps to reproduce?
Providing a StackBlitz/Plunker (or similar) is the *best* way to get the team to see your issue.

Plunker starter (using on `@master`): https://goo.gl/DlHd6U

StackBlitz starter (using latest `npm` release): https://goo.gl/wwnhMV

Just add a datepicker component

#### What is the use-case or motivation for changing an existing behavior?
Maybe user wants to type date instead of selecting form calendar.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
@angular/cli: 1.3.0
node: 6.10.3
os: darwin x64
@angular/animations: 4.3.5
@angular/cdk: 2.0.0-beta.8
@angular/common: 4.3.5
@angular/compiler: 4.3.5
@angular/core: 4.3.5
@angular/flex-layout: 2.0.0-beta.8
@angular/forms: 4.3.5
@angular/http: 4.3.5
@angular/material: 2.0.0-beta.8
@angular/platform-browser: 4.3.5
@angular/platform-browser-dynamic: 4.3.5
@angular/router: 4.3.5
@angular/cli: 1.3.0
@angular/compiler-cli: 4.3.5
@angular/language-service: 4.3.5

#### Is there anything else we should know?

リンクされている StackBlitz または Plunker の例を使って、まず date picker コンポーネントでリクエストを再現します。date picker の入力動作を確認し、想定されている入力方法、マスキング、パース、カレンダー操作を特定します。完了とは、ユーザーがカレンダーから選択せずに、正しい形式の日付を入力できる状態です。

索引モデルが issue の本文から書いたものです。