Improve how Document paths are compared

PathComparator sorting should be representative of the tree structure.

Actually, a structure with 2 folders "foo" and "foo.123" with their respective child will be sorted like that

• /foo
• /foo.123
• /foo/bar
• /foo.123/bar

This is not usable because we loose the hierarchy between parents and children. The order should be

• /foo
• /foo/bar
• /foo.123
• /foo.123/bar