Add docs about ga4gh_client package
Add docs about ga4gh_client package

Issue #1419

david4096/ga4gh-server,david4096/ga4gh-server,ga4gh/server,saupchurch/server,ga4gh/server,dcolligan/server,dcolligan/server,saupchurch/server,ga4gh/server,david4096/ga4gh-server,dcolligan/server,saupchurch/server