Log Message:
sysutils/bkt: update to 0.8.0

What's Changed
 -  --ttl is now a required flag. Historically it arbitrarily defaulted to one
    minute; to preserve this behavior you can set BKT_TTL=1m in the environment
    that's executing bkt (#48 and #27)
 -  Swapped from Instant to SystemTime for TTL arithmetic and related operations
    (#45)
 -  Scopes are now base-64 encoded to support scope names that don't happen to
    be valid file names (#51)
 -  Improve error message on permission failures (#35)

API Changes
 -  CacheStatus::Hit(Instant) has been replaced with CacheStatus::Hit(SystemTime)