[HttpCachingBridgeAbstract] Add duration parameter to 'get_cached'
[HttpCachingBridgeAbstract] Add duration parameter to 'get_cached'

This allows to specify the cache duration for a specific
url without the need to delete the cache file first.
Instead the cache file is automatically deleted if the
duration elapsed.

griffaurel/rss-bridge,ORelio/rss-bridge,ORelio/rss-bridge,LogMANOriginal/rss-bridge,LogMANOriginal/rss-bridge,RSS-Bridge/rss-bridge,polo2ro/rss-bridge,Frenzie/rss-bridge,sebsauvage/rss-bridge,Riduidel/rss-bridge,teromene/rss-bridge,mro/rss-bridge,Riduidel/rss-bridge,teromene/rss-bridge,Riduidel/rss-bridge,simonbru/rss-bridge,ORelio/rss-bridge,kranack/rss-bridge,mro/rss-bridge,simonbru/rss-bridge,kranack/rss-bridge,kranack/rss-bridge,GregThib/rss-bridge,Frenzie/rss-bridge,RSS-Bridge/rss-bridge,kranack/rss-bridge,RSS-Bridge/rss-bridge