revamp of log config db (and fix a crash in save_log_config_entry)

DB changes:
. "audit_status" field was changed to a more generic "distrusted" field
. audit status is now represented with a time range (within which the
  log is trusted)
. the log_id can now be used for configuration

Only the minimum changes to allow using the new DB format were made
to mod_ssl_ct.  IOW, it can't yet use the new information, and
the CTStaticLogConfig directive can't be used to configure the new
information either.