NCNN backend : add inputblob and ouputblob option to mllib at service creation time

[fantes]

when omitted, previous hardcoded default are used

example usage:

curl -X PUT "http://10.10.77.61:"$1"/services/lieb_test" -d '{
  "mllib":"ncnn",
  "description":"input output blob test",
  "type":"supervised",
  "parameters":{
       "input":{
          "connector":"csvts",
          "db": false,
      "label" : ["out1","out2","out3"],
      "ignore": ["time"]
       },
       "mllib":{
            "inputblob":"data",
            "outputblob":"rnn_pred",
            "gpuid" : 1,
            "db": false
        }
  },
  "model":{
      "repository":"/path/to/repo"
  }
 }'

[beniz]

hudson.plugins.git.GitException: Command "git merge cf4b31946f8543e64005419ab616f0797e40c117" returned status code 1:

stdout: Auto-merging src/backends/ncnn/ncnnlib.cc

CONFLICT (content): Merge conflict in src/backends/ncnn/ncnnlib.cc

Automatic merge failed; fix conflicts and then commit the result.

This may need a rebase to master.