add easy-to-use shortcuts for global queues
add easy-to-use shortcuts for global queues

piv199/EZSwiftExtensions,piv199/EZSwiftExtensions,astrokin/EZSwiftExtensions,goktugyil/EZSwiftExtensions,goktugyil/EZSwiftExtensions,kirakik/EZSwiftExtensions,kirakik/EZSwiftExtensions,astrokin/EZSwiftExtensions