basicfuncs: Add $(or) and $(padding) template functions

Migrated over from the Incubator, this adds the $(or) and $(padding)
template functions, with tests included.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
graphite: New module, graduating from the Incubator

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
riemann: New destination, graduating from the Incubator

This adds a new destination, to forward metrics to Riemann. The module
graduated from the Incubator, and has been adapted to syslog-ng 3.6
conventions and features.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
.travis.yml: Add Riemann support too

Add the 3rd party repository that has a riemann-c-client backport, and
install libriemann-client-dev, so that the riemann destination gets
compiled too.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #217 from algernon/f/3.6/incubator-migration

Graduate a few things from the Incubator