Miscellaneous:Reminder Message about saving OPJ as OPJU

Version: 2018

Type: Features

Category: Miscellaneous

Subcategory: Origin Workspace

Jira: ORG-16834

When user opens an OPJ file and later Save As, by default the format is OPJU, and we should open a reminder message box to inform them earlier version of Origin will not be able to open such files and allow Cancel, so file not saved.