Gives more accurate error propagation, control of depth of recursion
and short circuit recursion where possible.
Most of the the heavy lifting is done in the "fs" package, making file
system implementations a bit simpler.
This commit contains some code originally by Klaus Post.
Fixes#316
...unless had some errors or stats interval requested.
Add fs.ErrorLog to differentiate between Logs which should be
suppressed and errors which shouldn't.
