tidy graphics of version selection
fix javascript for cookies, and extend it to allow turning on/off all warnings (clear cookie or set master cookie)
Merge remote-tracking branch 'jdtoy/version-warning' into version-warning

Conflicts:
	docs/_layouts/page.html -- both fixed links, i modified text too
Merge pull request #1 from ahgittin/version-warning

tweak text and colours, add links for enabling/disabling warnings