[examples] Time.Seconds property

To use it for testing polling with different intervals

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[server] use proper property permissions

read/write access is based on property information

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[server] enable rw access

enabling ability to change statefs property

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>