Organize HTTP and GRPC response streaming together in LMI section

[lxning]

📚 The doc issue

There are 2 instruction links for streaming support in TS.

• GRPC response streaming : https://github.com/pytorch/serve/blob/master/docs/grpc_api.md#grpc-server-side-streaming
• Http response streaming: https://github.com/pytorch/serve/blob/master/docs/inference_api.md#curl-example-1

It is not easy for user to find this feature when they run LMI.

Suggest a potential alternative/fix

Add a section streaming support in LMI doc to include the HTTP and GRPC information.

[sekyondaMeta]

The PR below adds this information to the LMI doc and cleans it up as well. There were some minor changes that Mark had requested and most are done. @lxning feel free to review the PR and let me know if there is anything else you want added.
pr #2468