Add basic popup windows

* The message popup just shows a message to the user.
* The confirm popup shows a message and prompts the user to select
between different options (like yes/no).
* The text input popup shows a message and prompts the user to input
some text.
Add basic FileManagerProgram for file management

Add a basic file manager desktop program that allows viewing and
managing the files on all mounted file systems of the user's computer.
Remove unnecessary throws clause from Def.HandleInvoc.ProviderExt.Test

Remove an unnecessary throws clause from the
DefaultHandleInvocationProviderExtensionTest class.