Update README and course front page to mention HOL014

[flozanorht]

I cannot do this before the HOL017 labs+ classroom is pushed into production. Right now it's available only on ROL-factory, which is NOT acessible to learners.

[flozanorht]

HOL014 was released and verified in production, then pulled back because of concerns from GLS. Now I'm waiting for it to be made available again.