fix "Cannot parse value line" errors because rrd_strtodbl cannot handle "-nan"
Fix rrd create via cached - file name sanitation (absolutation?)
did quietly assume that files would have to exists. Which ist not
quite right for many "create" usecases.
fetch data from cached with full double precision to make sure results
obtained with and without rrdcached are the same.
This might be deemed to high a cost, because the line protocol now carries
up to 70% more data
Fix NULL pointer dereference error introduced during get_path "fixing"
Merge pull request #535 from stamfest/more-tobi-fixes

More tobi fixes