Don't use /Shared as a base for links in share email

I noticed that all share email notifications base to /Shared.

Added scrollto=$filename to the url, but also noticed this has been commented out for quite a while, can't think why: https://github.com/owncloud/core/commit/9d38e3602b2faf37d861729c52690ce51b8fee97

@PVince81 ^ ?

@karlitschek