Add an 'extractor_error' download state.
Add 'extractor_error' value to download_state enum.

Fix downloads marked as error when the problem was with the extractor not the download itself.
set the download stat to 'extractor_error' instead of 'error'
updated Vagrant documentation regarding running instances on EC2
Merge branch 'master' of github.com:berkmancenter/mediacloud
Merge branch 'master' into perl_5_18