[Documentation]Add Documentation for Install and use.

Currently, the documentation for Testgrid is very high level and does not have an "Installation and usage" section similar to kind's https://kind.sigs.k8s.io/.
The info provided lacks the implementation details to get a quick start with open source tools to setup the Testgrid backend. More specifically, we need the exact commands to do the following:

1) How to Install, build and run the testgrid instance running on localhost.
eg:- bazel build -options
/BUILD_PATH/testgrid -options
2) A sample run of how e2e tests can report against the backend server we brought up in (1).
3) OSS DB service we can use instead of google cloud storage.What schema we need etc.

Nice to have:
1) how to deploy this as an app on a k8s cluster.
2) An example of how we can customize a front end to consume the OSS Testgrid backend.