Default result backend should be "amqp"

Also, fix the broken blank postcard generator.
merge requirements
Merge branch 'master' of /git/btbv2
Merge branch 'master' of /git/btbv2
Merge branch 'master' of /git/btbv2
Merge branch 'master' of /git/btbv2
Merge branch 'master' of /git/btbv2
Add 'who does transcriptions' question