Develop RDF4J IO

[Eclipse RDF4J](http://rdf4j.org/) is a set of libraries for processing and handling [RDF](https://en.wikipedia.org/wiki/Resource_Description_Framework) data. The issue suggests to develop the following:

* transforms to read from the filesystem in all supported formats,
* transforms to write back to the filesystem in any supported formats,
* coders to be able to move RDF between transforms.

Partial implementation is available (in Kotlin) at https://github.com/DataFabricRus/scylla-beam-pipelines/blob/master/src/main/kotlin/cc/datafabric/scylladb/pipelines/io/RDF4JIO.kt

Imported from Jira [BEAM-6717](https://issues.apache.org/jira/browse/BEAM-6717). Original Jira may contain additional context.
Reported by: kolchinmax.