Installing the new Google Now Launcher (on any Android device)

The Google Experience Launcher, as it was, first arrived exclusively for the Nexus 5 towards the end of last year. That changed recently when the renamed Google Now Launcher (GNL) appeared in the Play Store as a standalone app for Nexus devices and those handsets running Google Play Edition (GPE), or to put it another way this is for Stock Android only. Unless you are prepared to fiddle a bit, that is...