all: consolidate configuration for coordinator and gomote

buildenv.Environment type defines configuration options:

- Coordinator uses the GCE project name to lookup config. A custom
  config name can be provided at runtime to override.

- The conventional prod and stage project names ('symbolic-datum-552'
  and 'go-dashboard-dev') map to prod and staging configuration structs.

- Production and staging status is explicitly defined in configuration.

- GCS bucket names for buildlet, logs, and snapshots are
  configurable.

Change-Id: I7e6d7874eb0bdfe35dbdd5fcf6212ab50d576b88
Reviewed-on: https://go-review.googlesource.com/19502
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
8 files changed