feat(grid-list): add header and footer support

[kara]

r: @jelbourn

This PR adds header and footer support to grid-lists.

Example use:

<md-grid-list cols="3">
   <md-grid-tile *ngFor="let image of images">
      <md-grid-tile-footer>
           <h3 md-line> Title </h3>
           <span md-line> Description </span>
           <md-icon>star_border</md-icon>
      </md-grid-tile-footer>
    </md-grid-tile>
</md-grid-list>

[jelbourn]

Can the variables be gridlist instead of grid? Many people refer to 'data-table" as "grid", so I want to avoid confusion.

[kara]

Oh, good catch. I can change.

[kara]

@jelbourn Comments should be addressed

[jelbourn]

Format should be

/**
 * Helper that watches the number of lines in a text area and sets
 * a class on the host element that matches the line count.
 */

[jelbourn]

(here and for other block-style comments)

[kara]

Comments are hard

[jelbourn]

LGTM aside from comment format

[kara]

Fixed comment formatting. Merging!

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}