New NSNotifications for Receive and Load variables

* `LQDidReceiveValues`
* `LQDidLoadValues`

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Auto identifying an user on first event track

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Changing names of error messages levels

* kLQLogLevelDataPoint -> kLQLogLevelInfo
* kLQLogLevelEvent -> kLQLogLevelInfoVerbose

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Renaming destroySession method to destroySessionIfExists

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Use very first NSDate on first event

When tracking the very first event (`_startSession`) we're now using
date of first launch of the SDK instead of using the date of event.

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Auto adding an anonymous field to Users

If an user is identified using an auto identifier, this field will be automatically set to `true`, otherwise will be set to `false`.

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Small fix on (debug) logging messages

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>