Breaking changes coming in Kibana v8

[Tenzer]

First of, thank you for making Logtrail!

I have just upgraded Elasticsearch and Kibana in a cluster, and noticed that it outputted the following message when it started up:

{"type":"log","@timestamp":"2020-11-11T16:59:50Z","tags":["warning","legacy-service"],"pid":7,"message":"Some installed third party plugin(s) [logtrail] are using the legacy plugin format and will no longer work in a future Kibana release. Please refer to https://ela.st/kibana-breaking-changes-8-0 for a list of breaking changes and https://ela.st/kibana-platform-migration for documentation on how to migrate legacy plugins."}

I couldn't immediately see any other issues about this, so I thought I would create one just to make sure you are aware of this.

[sivasamyk]

@Tenzer Thanks. I am aware of these changes. Based on my initial analysis it requires more effort to migrate logtrail to kibana 8.x. I am yet to find time to start this migration.