- correct documentation of default of raw image interleave read

 - correct documentation of default of raw image interleave read
   parameter
   https://rt.cpan.org/Ticket/Display.html?id=42074

 - add raw_ prefix to raw read parameters, though the original names
   still work.

 - fail the read if an invalid raw_interleave parameter is supplied

 - warn if no interleave or raw_interleave parameter is supplied,
   since the documented default was wrong, and incompatible with the
   write format

 - for reading raw images, if raw_storechannels > raw_datachannels,
   set the extra channels in the image to 0