[APNS] Cached to avoid null value on first data point

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[UniqueNow] Copy date object on uniqueNow: call

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Queue] Change tasks order when going bg to avoid wrong dates

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Delegates] Move bg tasks to applicationDidEnterBackground:

Move background tasks from `applicationWillResignActive:` to `applicationDidEnterBackground:`,
and used `beginBackgroundTaskWithExpirationHandler:` to extend background tasks time.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Sessions] No more limit of session time

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Reidentify] rename method aliasUser:

`aliasUserWithPreviousAnonymousUser:` changed to `aliasUser:`

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Session] Ending session on applicationWillTerminate:

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Delegates] Move fg tasks to applicationWillEnterForeground:

Moved all stuff from `applicationDidBecomeActive:` to `applicationWillEnterForeground:`

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Sessions] Complete refactor of start/end session handling

The same behaviour, with a different code organization.
More easy to read and to maintain.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Queue] Deprecate flush on background

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Refactor] Move primitive types initializers to Liquid init

Moved `sessionTimeout`, `queueSizeLimit` and `flushInterval` from lazy
initialization to Liquid init.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Delegates] applicationWillTerminate: really ending session

and not just tracking `_endSession` event.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Demo] Change data types of User "age" attribute

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[User] Avoid creating a new session if identifying two

times consecutively with the same User Unique ID.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Event] No need to auto identify on track: anymore

because user is always auto identified when Liquid is initialized.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Log] Small fix on user identify logging messages

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Reidentify] Rename internal method aliasUser:

Change `reidentifyUser:withIdentifier:` method to `aliasUser:withIdentifier:`

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Device] Renome unused @synthesize apnsToken

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>