Added bool Timeline::empty() method.

Mirrors std::container empty methods and is a useful counterpart
to the existing getNumItems(). Makes it easy to wait for animations
to complete before processing certain actions:
// e.g. in an update loop, don't process things if animating:
if( mSpecialTimeline.empty() )
{
 processSpecialItems();
}
Merge pull request #288 from sansumbrella/timeline_additions

Added bool Timeline::empty() method.
Minor fix to Box2D CinderBlock
Build fix for MotionBasic sample
fix linker error, link to QuickTime.framework

QuickTime symbols were spewed at link time on Xcode 4.6 / 10.8.2
Merge pull request #290 from pizthewiz/location-sample

fix linker error, link to QuickTime.framework
Fixing iOS samples/LocationManager build errors
Adding LocationManager to Mac AllSamples
Minor iOS sample build fixes
Adding missing samples to iOS AllSamples