add datasets APIs impl, and various improvement of PyFi

1. add datasets APIs: dataset download/import, and dataset manifest i… …
…mport

  a. dataset download: fifo datasets dataset <uuid> get (NOT TESTED, block by FiFo bug)
  b. dataset import: fifo datasets dataset <uuid> put --upload <dataset-gz>
  c. dataset manifest import: fifo datasets post --upload <dataset-manifest>

2. verbose mode for cmd line, -v

3. super cool feature: fifo --curl <any-cmd> will print the curl synopsis!

4. replace tabs with spaces in wiggle.py, added vim modelines

5. isolate the apiEndpoint, make the apiVersion configurable and assignable in cmd line