[Dialog] Allow customization of open/close animations

[Howard-Song]

Bug, feature request, or proposal:

feature

What is the expected behavior?

When open or close dialog,animation should define by developer.

What is the current behavior?

I found that open and close dialog <mat-dialog-container></mat-dialog-container>will add class ng-animating,well open will add once and remove within a short time period(less than 0.5s),but in my case,open and close will use different animation,so it doesn't work for me to overwrite .ng-animating

What is the use-case or motivation for changing an existing behavior?

Add different animation in open and close dialog.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Angular: 5.0.0,
Material: 5.0.0-rc0,
OS: win10,
TypeScript: 2.6.1,
Browsers: Chrome@62.0.3202.94

[swftvsn]

This should actually be implemented to all components that use animations.

A consistent way to override animations: by default provide animations that comply with material spec, but let developers override those with custom ones.

[bkandoori]

This is a very useful feature , it will be great if we can add the support.