Force UK Certification

[GoogleCodeExporter]

Add logic to scraping for when a movie does not contain UK certification 
ratings (movie only contains US) to perform a rough conversion from the US 
rating back to UK.

Possible conversion rate US -> UK -
G -> U
PG -> PG
PG-13 -> 12A
R -> 15
NC-17 -> 18
X -> R18

There is overlap hence no perfect conversion can ever really take place but I 
believe this is the best where no other information can be scraped.

Also add an option for this to be turned on and off in the plugin settings 
(Attempt conversion of rating to UK BBFC where none exists).

Thanks!

Original issue reported on code.google.com by thebatf...@gmail.com on 14 Apr 2012 at 9:54