riemann: Increase default TTL to 30

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
riemann: Better clock skew event generation

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
riemann: Split the config up into smaller parts

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
riemann: Final(?) clock-skew change

Only calculate clock skew for events that have a host, and tag them
internal.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>