[OC-4235] 'delay-loading' changes to reduce load-time

Here are findings, load-time differences before & after code changes.

# knife-core(no-plugins)
		real 	0m0.744s
		user	0m0.688s
		sys  	0m0.052s

# knife(with knife-google, knife-hp, knife-ec2, knife-windows, knife-terremark, knife-bluelock, knife-ec2)
	# Before  changes, 
		real 	0m4.360s
		user	0m3.464s
		sys  	0m0.280s

	# After changes, 
		real 	0m1.738s
		user	0m1.640s
		sys  	0m0.076s

Environment:
1. Chef Version: 10.14.2
2. Ruby Version: 1.9.3p194
3. Gem Version: 1.8.24