Add array.set, array.append and array.remove

scripts to help update arrays inside documents.
For example:

curl -XPOST http://localhost:9200/test/type/1/_update -d { \
  "script": "array.set", \
  "lang": "native", \
  "params": { \
    "source": "tags", \
    "values": [ \
      "elasticsearch", \
      "wow", \
      "lah" \
    ] \
  } \
}