Partially reverted the commit 81ac55bfd40d6fc04dfe3ac97db4ed6359a6d6be

Partially reverted the commit 81ac55bfd40d6fc04dfe3ac97db4ed6359a6d6be
The Expires header coming in the initail subscription gives us the correct
value to schedule the resubscription.
So we don't need to parse the subscription-state header, because only works for
give us the remaining time for each subscription.
But how the batched subscription process back only one answer for many contacts
we need to split in two parts: for single and batched subscription contacts respectively.

Also were commented the extra headers in INVITE, including them sometimes the
server backs the 500 Server Internal Error. I will check this problem.