* Adds Dialog support for `minWidth`, `minHeight`, `maxWidth` and `maxHeight` via config. Mostly delegates to Overlay.
* Moves declared `max-width` on `. mat-dialog-container` stylesheet to be authored via `MatDialogConfig`, providing the same default `80vw` value. Without this change, there would likely be undesired layout results due to different constraints being set on the overlay container vs the nested the dialog container.
* Added note on `minHeight` and `maxHeight` regarding the potential need to also set a `height` due to the rules around computed height resolution (https://www.w3.org/TR/CSS2/visudet.html#min-max-widths).  Any value set on `height` as a default would probably be assuming too much and may have varying results across browsers.

Not adding `minWidth`, `minHeight`, `maxWidth` and `maxHeight` to `config` to avoid overriding the default value of `maxWidth` particularly—the type checker will require it to be a string. Instead, setting `config` to type `MatDialogConfig` is prefered to appease the type checker since those four properties are optional.

Appeases the AOT type checker for the template by extending `MatDialogConfig` to disallow `position` from being undefined, given that it’s optional. Guards cannot be set on the template because the values are bound to NgModel.

…axHeight