make write_file public
add rrd_modify (but do not yet use it)
make modify command available
- so far it is only really possible to remove data sources
Refactor all DS definition parsing code. It was not reusable and tied
too much to the rrd_t data structure.
Allow to add data sources to an RRD
Extend rrdcached client API to be able to also send FORGET and other
filename based commands easily
provide new write_fh function
streamline and clean up
Add some documentation
rrdcached handling
Add documentation for modify command
Merge pull request #447 from stamfest/rrdmodify-master

Rrdmodify master