Add datasets list command.
Add datasets get command.
Add datasets delete command.
Grep for something else instead of page token.

Apparently, this page token is not fixed. So we should grep for
something else.
Remove some line wraps.
Use prepared files from google-api-go-client project.

We used to generate the API ourselves. This commit switches to use an
upstream version from code.google.com/p/google-api-go-client/genomics.