Merge pull request #5 from deztructor/reliability

Handle no-sim correctly, no races during status updates
[ofono] monitor network properties changes before retrieval

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[ofono] check interfaces instead of features

Features cover only part of Interfaces, so for extensibility reasons
work with Interfaces

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[ofono] do not reset interfaces if they are null

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[ofono] Call forwarding state is exposed

Set of tristate [0, 1, "" (unknown)] properties: ForwardUnconditional,
ForwardBusy, ForwardNoReply, ForwardNotReachable. Phone number is not
exposed now for privacy reasons.

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