Add Flash - High to default BBC formats

Necessary for audio described and signed versions
Fixed get webpage parsing
Replaced invalid get_iplayer argument
Updated get_iplayer.pl to 2.87
Set uniform environment for get_iplayer invocations
No need for --fatfilename any longer
Added support for downloading programmes older than 7 days

Programmes older than 7 days can be downloaded via "Use Current Webpage"
or "Process PID".  PIDs not found in cache will be looked up with
get_iplayer --info --pid=<PID> (requires get_iplayer 2.87+).