Arrays support

[boguslavsky]

Add support of Arrays with following syntax:

      var Arr = Exonum.newArray({
        size: 8,
        type: Exonum.Uint64
      })
      var Type = Exonum.newType({
        size: 8,
        fields: {
          list: {type: Arr, size: 8, from: 0, to: 8}
        }
      })
      var data = {
        list: [
          167,
          102851,
          22210,
          724
        ]
      }
      var buffer = Type.serialize(data)

[coveralls]

Coverage increased (+0.7%) to 90.983% when pulling 4600be6 on boguslavsky:arrays into a1d9d3d on exonum:master.

[coveralls]

Coverage increased (+0.7%) to 90.917% when pulling d831de1 on boguslavsky:arrays into effa88b on exonum:master.