the first version of Umbrella

Umbrella is a tool for specifying and materializing comprehensive execution environments, from the hardware all the way up to software and data.  A user simply invokes Umbrella with the desired task, and Umbrella determines the minimum mechanism necessary to run the task, whether it be direct execution, a system container, a local virtual machine, or submission to a cloud or grid environment.  

Test Cases:
Current there are two test cases, one is for cms application and the other for povray application.
The test cmd is in the file named `cmd`, and the corresponding specification files are under `json_dir`.

All the following work is listed in `todo_list`.