Speedup resolver when useCache is enabled

The str() formatted flavor of a trove tuple was used in a cache key,
which triggered the full thaw of the flavor instead of leaving it in its
lazy form. Using freeze() instead avoids triggering the thaw at all and
saves a few seconds of needless parsing.
Minor cleanups in resolvesource in preparation for some speedup work
Pre-cache resolveTrove dep information when resolving
Enable reuse of partially matching btrfs chroots
Add btrfs-tmpwatch tool
Always use the configured Conary proxy when building
Update copyright/license on some files that got missed
btrfs: fsync after creating the lockfile to avoid an odd race
chroothelper: terminate chrootserver if parent goes away