Support Kibana index-pattern fieldFormatMap

[richm]

With Kibana index-patterns, you can define how fields are displayed. For example, for Number bytes, you can choose to display the field in Bytes, which will display the value as e.g. 100K, 2.4M, 1.34G

For namespaces, when defining a value, there should be a format field which takes as a value one of the format types supported by Kibana (see the Settings tab). Some formats take additional parameters - for example, the truncated string type takes the length as a parameter. These should be specified as the formatParams value e.g.

    - name: vm_disk_write_bytes
      type: long
      description: >
        collectd's disk_write_bytes type of statsd plugin.
      format: bytes

  - name: trimmed
    type: string
    description: >
      An array of JSONPath expressions relative to the event object,
      specifying objects/arrays with (some) contents removed as the result of
      event size limiting. Empty string means event itself. Empty array means
      trimming occurred at unspecified objects/arrays.
    format: truncate
    formatParams:
      fieldLength: 47

Would be converted to fieldFormatMap like this:

"fieldFormatMap": "{\"collectd.statsd.vm_disk_write_bytes\":{\"id\":\"bytes\"}, \"aushape.trimmed\":{\"id\":\"truncate\",\"params\":{\"fieldLength\":\"47\"}}}"