Allow filtering absolute paths
Allow filtering absolute paths

Before, the restorer called the filter function with a relative path,
this prevented anchoring absolute patterns (which just never matched).
Now call the restore function with an absolute virtual path, starting at
the filepath separator.

Closes #834

jayme-github/restic,stuertz/restic,restic/restic,middelink/restic,restic/restic,ar-jan/restic,byo/restic,kurin/restic,fawick/restic,byo/restic,kurin/restic,ar-jan/restic,middelink/restic,stuertz/restic,fawick/restic,jayme-github/restic