Fix cleanPath/getItemURL not encoding single quotes

This was causing issues with user-provided filenames in Sharesome: https://github.com/skddc/sharesome/issues/30

I pinned it down to `cleanPath` in `WireClient`, which I moved to `RemoteStorage.util` and fixed there. Working fine now, and the patched version is already running on https://sharesome.5apps.com/
You are not supposed to declare the same variable twice. `itemURL` has been declared 3 lines above already. The `var` in this line should be removed.