New annotation for external metadata in R scripts

[nuest]

Create a new annotation: #wps.metadata that takes a path (relative to the script file, see if things like ../ work, absolute) to a file with the annotations, if annotations and code are to be kept separate. This would allow to keep the R script file itself cleaner.

@autermann: In the (very very) long run this would facilitate an annotation framework for scripting languages within the 52N WPS which might even allow to use YAML annotation files for R scripts :-).