Add DanceDance governor (Thanks to Shaun Nuzzo)

Conflicts:
	include/linux/cpufreq.h

Conflicts:
	include/linux/cpufreq.h
block: Add VR I/O scheduler

Conflicts:
	block/Kconfig.iosched
	block/Makefile
block: Add ZEN I/O scheduler

Conflicts:
	block/Kconfig.iosched
	block/Makefile