feat(mdPanel): Wrapper and Panel elements referenced in the MdPanelRef

[bradrich]

Actual Behavior:

• What is the issue? *
• There is not a reference to the Wrapper and Panel elements within the returned MdPanelRef.
• What is the expected behavior?
• A jqLite reference of the Wrapper and Panel elements should be returned within the MdPanelRef object. Then several functions, i.e. addClass, removeClass, etc., could be run on the elements without having to have these type functions repeated within the MdPanel API.

CodePen (or steps to reproduce the issue): *

• CodePen Demo which shows your issue: N/A
• Details: N/A

Angular Versions: *

• Angular Version: Latest
• Angular Material Version: Latest

Additional Information:

• Browser Type: * All
• Browser Version: * Latest
• OS: * All
• Stack Traces: N/A

[bradrich]

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