SiloOrigin.openDocument() bypassed open_item() when a local file
existed, skipping dependency pulling for assemblies. Silo_Pull also
skipped dependency pulling when no revisions had files but a local
file existed.
Changes:
- SiloOrigin.openDocument(): remove local-file shortcut, route all
opens through open_item() which already handles dependency pulling
- Silo_Pull.Activated(): add _pull_dependencies() call before opening
existing local assembly files in the no-revisions-have-files path
Closes#337