[Alert component] Make it undismissible by default

[robbieaverill]

This renders an alert which is dismissible, since I didn't tell it not to be, but the close button has no default handler. This feels strange to me, I think we should make it undismissible by default.

[ScopeyNZ]

Yeah good point. We can maybe be fancy here and use this.$listeners.close to figure it out.

Also, I notice that the click event is bound to the icon and not the button which is wrong, so we should fix that too.