Add "Delete Model" menu entry

Doesn’t do anything yet, though.
Fix issue with model component overwriting class component

A copy was needed. Sneaky pass-by-reference in JavaScript.
Add generic cancel button handler to model menu

Now any dialog that sports a “Cancel” button will go here when the
button is clicked.
Add event handlers for "Delete" button in model menu

Also added FA icons to the default “OK” and “Cancel” buttons displayed
on menu dialogs.
Rename OpenDialogBox DroplistDialogBox
Fix error with FA icon string showing in tooltip
Update sample hydrotrend.json file