http: Add MIME type support for JSON
http: Add MIME type support for JSON

JSON is used in the API and it should be mapped to 'application/json'
MIME type. Currently, it is not mapped to anything and therefore the
default text plain type is used.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@scylladb.com>
Message-Id: <20170821123916.5278-1-ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@scylladb.com>

dreamsxin/seastar,cloudius-systems/seastar,avikivity/seastar,dreamsxin/seastar,cloudius-systems/seastar,syuu1228/seastar,cloudius-systems/seastar,avikivity/seastar,scylladb/seastar,scylladb/seastar,syuu1228/seastar,syuu1228/seastar,scylladb/seastar,avikivity/seastar,dreamsxin/seastar