Keep support to "skipHide" with a deprecation warning

[Liz4v]

Actual Behavior:

1. Upgrade build version from 1.1.1 to 1.1.3
2. Breaking change: $mdDialog.show({skipHide: true}) stops working because it was renamed to multiple. (See dialog: skipHide not working #10076)

Expected Behavior:

1. Upgrade build version from 1.1.1 to 1.1.3
2. Rename should generate a deprecation warning, but keep working for the full ~1.1.1 branch forever.

[LoganLehman]

Agreed. This needs to happen so things don't break immediately.

[arcreative]

...glad I noticed the errant behavior. This is a pretty big deal and breaks a lot of things in my app.