supports reindex

[po3rin]

supports reindex.
https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html

index:
  # ...

  # reindex test-v1 -> reindex-v1	
  - name: reindex-v1
    mapping: testdata/test.json
    reindex:
        source: test-v1 
        slices: 3 # default=1
        waitForCompletion: true # default=false
        # 'on' field supports 2 hooks.
        # 'reindex': only when index is created for the first time.
        # 'always': always exec reindex.
        on: firstCreated