By Jay Kuehner British. Prison. Drama. Say it and sigh: Where can the genre go, post-Scum, Porridge, Bad Girls, Ghosted, Screwed, Hunger? Nonetheless, David Mackenzie (Young Adam) makes a gritty bid for the pantheon with this initially lean and suitably mean rendering of a typically corrupt prison system where inmates are predestined for internecine feuds and cigarettes, cellphones, and verbal…