download page enhancements (BB-687)

would be nice to have a way to group downloads along with a description. something like:

{{{
release 0.4.0 (3 files)
this is the 0.4.0 release of the xyz project and incorporates many feature improvements.....

• xyz-0.4.0.zip 2.0mb downloaded 4 times
  
• xyz-0.4.0.tgz 1.7mb downloaded 5 times
  
• xyz-0.4.0.bz2 1.5mb downloaded 110 times

release 0.3.0 (3 files)
some description...

• xyz-0.3.0.zip 1.8mb downloaded 99 times
  
• xyz-0.3.0.tgz 1.5mb downloaded 98 times
  
• xyz-0.3.0.bz2 1.3mb downloaded 97 times
  }}}

if they were collapsible that would be nice too