Add support to cbt tool to drop all rows from a table.
Adds a method to update an instance with clusters.
Adds StorageType to ClusterInfo.
Add support for the -auth-token flag to cbt tool.
Adds support for Table-level IAM, including some bug fixes.
This is the first tag to carve out bigtable as its own module. See: https://github.com/golang/go/wiki/Modules#is-it-possible-to-add-a-module-to-a-multi-module-repository.