KIJIMR-58. Rework job builders and CLI tools.

 - Job inputs and outputs are specified using space-separated param maps from the CLI.
 - Job builders API uses KijiURIs to reference tables (avoid leaking Kiji and KijiTable).
 - JobInputSpec and JobOutputSpec are no longer.

Signed-off-by: Lee Sheng <lsheng@wibidata.com>