Allow specifying path for quota query

[PVince81]

In some environments like Nextcloud, the quota might not be the same depending on the path. This is because a user could have external storages mounted or received shares in which the quota of the owner would apply.

[PVince81]

At first I thought I can just do a stat and query the quota properties directly, but it's not possible to query custom props: #238

So will need to resort to "customRequest" and build the XML query on my own, not so nice.

[perry-mitchell]

Thanks @PVince81 - Do you know if quota is available on Nextcloud per route? Would be nice to have some sample output so I can turn this into a feature - in case anyone might contribute a snippet of XML.