1. add datasets APIs: dataset download/import, and dataset manifest import (partly tested)

  a. dataset download: fifo datasets dataset <uuid> get
  b. dataset import: fifo datasets dataset <uuid> put --upload <dataset-gz>
  c. dataset manifest import: fifo datasets post --upload <dataset-manifest>

2. and also add many verbose print in wiggle.py

3. super cool feature: fifo --curl <any-cmd> will print the curl synopsis!