query: Implement wrappers around Query

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
message: Support embedding a query within a message

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
src/riemann-query: Small utility to query Riemann

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