file based import/export of individual dashboards

- add support for simple export (to file) and import (from file) of kibana dashboards from/to elasticsearch
- add basic, naive converter for converting kibana dashboards from logstash event v0 to v1 style keys
prefix backup filename with hostname to allow multiple hosts to use the same bucket without conflict.
201 is also a success code for ES
Merge pull request #1 from pantheon-systems/kibana_migration

file based import/export of individual dashboards