* adjust GO_VERSION_OUTPUT_PAT to accept more forms of `go version` output
* handle appengine version as well
* do a real chdir to avoid the stored working directory going of sync
* use the new sh.env. fixes issues with gslint reporting build failures due to undefined GOPATH, etc.
* add an `echo` command
* expand env vars in the non-shell command line
* document the `echo` command
* update docs to reflect on the current state of the difference between `9o` and `sh` modes
* ann
* show the `go build` output when building margo
* show the output of `go version`
* ann
* add commands gs_open_dist_path and gs_open_home_path
* fix opening the wrong error log
* ann