3523

Add scripting functions for passwords and autoexport

Scripts, and agents driving TreeSheets over the agent socket, couldn't
open password protected documents without someone answering the dialog.
ts.load_document now takes an optional password, which is used instead
of asking; a wrong one makes it fail rather than prompt. ts.set_password
does the same as File > Set Password..., and ts.set_autoexport and
ts.get_autoexport change and read a document's autoexport options.