* Add options to Put, PutUnchecked and Update for all Fses
* Use these to create HashOption
* Implement this in local
* Pass the option in fs.Copy
This has the effect that we only calculate hashes we need to in the
local Fs which speeds up transfers significantly.
This works by making sure directory listings that use a filter only
iterate the files provided in the filter (if any).
Single file copies now don't iterate the source or destination
buckets.
Note that this could potentially slow down very long `--files-from`
lists - this is easy to fix (with another flag probably) if it causes
anyone a problem.
Fixes#610Fixes#769
