Handle weird characters in incoming paths

[pontus]

This is related to NBISweden/sda-cli#161. Similarly to what's suggested there out of niceness, server side this should be done to limit what can get passed on to the various backends.

I don't have any opinion on whatever this should be done in the storage backends (which presumably knows better what characters need to be removed) or in the main code (which might be simpler and might as well remove anything "weird").

With the currently deployed version for BP with the current sda-cli release, it seems uploading when giving a full path (e.g. sda-cli -c s3cmd.conf -r C:\some\thing) breaks because the backend storage does not like the generated object paths.