azdev extension/cli create -- additional functionality

So this is a proposal to add new parameters to the command:

**--autorest-input-file (json or md file within locally cloned azure-rest-api-specs)**

If the parameter is added, **azdev** would run following docker command:

docker run -ti -v **azure-rest-api-specs-folder**:/azure-rest-api-specs -v **output-folder**:/generated zikalino/autorest.devops /azure-rest-api-specs/**path-to-md-file**.md **azdev**

The command will produce following files in **output-folder**:
- _client_factory.py
- _help.py
- _params.py
- commands.py
- custom.py
- report.md

These files can be used to replace scaffolded files with complete prototype implementation of command module.