[receiver/gelfreceiver] Add support for GELF receiver for logging

[BharatKJain]

Important (read before submitting)

I have added the code for GELF receiver, please follow this PR.

Is your feature request related to a problem? Please describe.

We're using GELF based logging for all application logs, which have a GELF client in them - refer to go GELF client.

We want to support server-side reception for GELF based logs.

Describe the solution you'd like

Please check the PR

Describe alternatives you've considered

We're already using the tremor's implementation of GELF - link to tremor docs

Additional context None