fix HTTP MR error reporting

These case clauses haven't matched since the 1.3 release, if my
testing is correct. This patch reinstates use of
riak_kv_mapred_json:jsonify_pipe_error to send useful JSON to
an HTTP client.
Merge pull request #639 from branch 'bwf-mr-http-errors' into develop
Remove duplicate make targets.
Merge pull request #647 from basho/csm-remove-dup-targets

Remove duplicate make targets.
Add dialyzer targets.
Merge pull request #648 from basho/csm-add-dialyzer-targets

Add dialyzer targets.
Add QC_OUT macro, my dots were being swallowed.
Merge branch 'develop' into feature/rdb-crdt-general
Add some types and docs, remove gcounter