Made Excel app to show during runtime
Remove unnecessary exceptions
Brought back OnCleanup event handler

for Excel app to save, quit and cleanup on Dynamo close.
Revert "Brought back OnCleanup event handler"

This reverts commit c705503a9811ee5e1d0784d8ba2bc62eede02742.
Merge pull request #1434 from ellensi/DSOffice

Quick fixes for DSOffice