Switch vagrant to Ubuntu 18.04 and make it work

Switch to ubuntu/bionic64, drop 32 bit support
Set the default for all timestamps in the user table to '1970-01-01 00:00:01' because the previously used value is illegal in newer mysql versions.
Fix migrations/20/issue_194_clear_old_newuser_tokens.sql - can not set token to null.
Fix choice of nextpinid in migrations/5/privileges.sql which failed for fresh databases
Generally get rid of lots of warnings and errors in the vagrant provisioning

vhs / nomos