Add warning message to Discard Changes button

[jmakowski1123]

When users click on "Discard Changes", display a warning and confirmation dialog before actually discarding changes.

The message should read:

Are you sure you want to discard all unpublished changes in this library? This will include changes made by other users.

[jmakowski1123]

@bradenmacdonald Is this something that can be added post code-cut?

[bradenmacdonald]

Oooh yeah we should put a confirmation on that. I suggest a warning confirm dialog would be better, like we're doing for "delete component":

(But it would say "Are you sure you want to discard all unpublished changes in this library? This will include changes made by other users")

[jmakowski1123]

Yes, agree and this looks good

[bradenmacdonald]

@jmakowski1123 @sdaitzman @lizc577 @marcotuts This is ready for acceptance testing on the sandbox.

[lizc577]

This looks good, I am noticing a fraction of a second delay in the message where it generates the title of the component in the delete message. not a show stopper, but thought it was worth noting