Alert http v1.2

Extends the JSON alert output to include the HTTP data,
added config option from previous PR: https://github.com/inliniac/suricata/pull/1081
This is something I actually missed in the payload logging patch, but this isn't the correct place to set flags (not for the payload/packet logging either).

The proper solution would be to implement whats discussed here: https://github.com/serializingme/suricata/commit/0154cedd772c871e6e03bc1f36ad38e9c3f50360#commitcomment-7209232