Feature completed:
* removed ability to specify whether client should trigger presence event during subscription / unsubscription or not
* added configuration property which allow to specify whether client should keep previous time token during channels list change or request new one

Fixed issues:
* demo app wasn't able to display information for PNClient in side table
* copied library into demo projects
* updated library information (debug output in console)
* tweaked time token update condition
* copied library into demo projects
* updated library information (debug output in console)
add test for leave
Tweaked:
* subscription restore logic (it will issue subscribe with 0 time token to generate presence event if required)

Fixed issue:
* presence observation caused library to "hang"
* copied library into demo projects
* updated library information (debug output in console)
Feature completed:
* send 'pnexpires' field along with heartbeat request
* copied library into demo projects
* updated library information (debug output in console)
Updated readme file and default state for flag
Merge branch 'origin/feature-pt66739978'
fixed unit test
Merge branch 'feature-pt66739978' into presence-v3

Conflicts:
	iOS/tests/iOSUnitTests/pubnub.xcodeproj/project.pbxproj
	iOS/tests/iOSUnitTests/pubnubTests/HeartbeatTest/HeartbeatTest.m
	iOS/tests/iOSUnitTests/pubnubTests/HeartbeatTest/MyPNConnection.m