viewer: Add compression to self-contained view server

This doesn't matter much when using it locally, but the database file
can be >100MB, which makes it painful over a remote connection.
fs_testgen: Increase to 16 datavals

Small lists ironically appear to require more datavals in testgen.
Raise the limit to 16 so we have two full files worth available.
fs: Model and testgen for sync, fsync, and reboot
fs_testgen: Cleanly skip testgen for functions we don't implement
spec: Support negation in function list argument
README: Point out how to skip test generation for unsupported calls
par-mtrace: Support running fstest from a non-ramfs file system
par-mtrace: Detect and warn about failed shards
README: How to run with a disk-based file system