[config] set user_allow_other option

There should not be security risk related to this option if filesystem is
designed properly (uses access control), just each fuse filesystems packaged for
nemo should be checked for potential security risks, e.g. filesystems like encfs
providing access to sensitive data, should be checked for proper access control

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>