Completed Changes
- User-visible: 
vesta/repos_ui/58: Make vcreate and vbranch always add a version 0
vesta/config/22: Keep vgetconfig -w from crashing when the setting isn't present
vesta/repos/101, vesta/repltools/34: Fix replication problems if "latest" gets ghosted
 - Low-level: 
basics/basics/41: Add Basics::mutex::trylock