Add a parameter to specify index direction

[daewon]

example)

{
...
 "indexProps": [
            {
                "indexName": "pk",
                "indexDirection": "both",
                "indexProps": [
                    {"name": "user_type", "defaultValue": "-", "dataType": "string" },
                    {"name": "action_type", "defaultValue": "v", "dataType": "string" },
                    {"name": "doc_type", "defaultValue": "-", "dataType": "string" },
                    {"name": "_timestamp", "defaultValue": 0, "dataType": "long"}
                ]
            },      
            {
                "indexName": "idx_2",
                "indexDirection": "in",
                "indexProps": [
                    {"name": "user_type", "defaultValue": "-", "dataType": "string" },
                    {"name": "_timestamp", "defaultValue": 0, "dataType": "long"},
                    {"name": "doc_type", "defaultValue": "-", "dataType": "string" },
                    {"name": "action_type", "defaultValue": "v", "dataType": "string" }
                ]
            }            
    ]
...
}

• out: out direction index only
• in: in direction index only
• both: out/in direction index

[SteamShon]

@hsleep I created new issue #116 for different index for label direction. so I think this issue can be closed.