azdev scaffolding commands and setup tweaks

[tjprescott]

Fixes #18. Fixes #63.

[tjprescott]

@zikalino @achandmsft here is the PR for the cli/extension create commands.

[zikalino]

@tjprescott thank you! it's pretty large, I will put some comments very soon.
I am actually wondering how we could do more with some additional information from swagger.

[tjprescott]

@zikalino we were planning to more seriously investigate auto-generation of commands from Swagger but decided this has value in its own right and is pretty low-cost.

I will likely add an interactive mode for this command (similar to azdev setup) to better walk newcomers through the process.

[zikalino]

@tjprescott I agree, I think we should definitely merge as it definitely creates very good framework that can be extended.

[zikalino]

that was something what was removed before, right?

[zikalino]

PR looks really good. I think it shoudl be merged.
Also very good reference for me on adding new command modules, so i want to use it asap :-)

[tjprescott]

Thanks @zikalino. I have a few final points that will add the right annotations to the CODEOWNERS file and some other little housekeeping items, but I hope to merge and release today or tomorrow.

[zikalino]

@tjprescott I forgot to mention, I used your branch and have tested it and it works for me!

[zikalino]

I forgot to mention one more thing.
I have generated apimanagement command, and there was one exception, to fix it I had to make change in one of the autogenerated files.

I didn't dig any further, perhaps my azure-cli code was out of sync or something like that...

/workspaces/azure-cli/src/command_modules/azure-cli-apimanagement/azure/cli/command_modules/apimanagement/commands.py

Just at the end of file i removed is_preview=True from following code:

    with self.command_group('apimanagement', is_preview=True):
        pass

The exception was:

The command failed with an unexpected error. Here is the traceback:

unrecognized kwargs: ['is_preview']
Traceback (most recent call last):
  File "/azure-cli/env/lib/python3.6/site-packages/knack/cli.py", line 206, in invoke
    cmd_result = self.invocation.execute(args)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/commands/__init__.py", line 439, in execute
    self.commands_loader.load_command_table(args)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/__init__.py", line 247, in load_command_table
    _update_command_table_from_modules(args)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/__init__.py", line 144, in _update_command_table_from_modules
    module_command_table, module_group_table = _load_module_command_loader(self, args, mod)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/commands/__init__.py", line 893, in _load_module_command_loader
    return _load_command_loader(loader, args, mod, 'azure.cli.command_modules.')
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/commands/__init__.py", line 875, in _load_command_loader
    command_table = command_loader.load_command_table(args)
  File "/workspaces/azure-cli/src/command_modules/azure-cli-apimanagement/azure/cli/command_modules/apimanagement/__init__.py", line 24, in load_command_table
    load_command_table(self, args)
  File "/workspaces/azure-cli/src/command_modules/azure-cli-apimanagement/azure/cli/command_modules/apimanagement/commands.py", line 26, in load_command_table
    with self.command_group('apimanagement', is_preview=True):
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/__init__.py", line 422, in command_group
    return self._command_group_cls(self, group_name, **kwargs)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/commands/__init__.py", line 989, in __init__
    merged_kwargs = self._merge_kwargs(kwargs, base_kwargs=command_loader.module_kwargs)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/commands/__init__.py", line 1013, in _merge_kwargs
    return _merge_kwargs(kwargs, base, CLI_COMMAND_KWARGS)
  File "/workspaces/azure-cli/src/azure-cli-core/azure/cli/core/commands/__init__.py", line 964, in _merge_kwargs
    raise TypeError('unrecognized kwargs: {}'.format(unrecognized_kwargs))
TypeError: unrecognized kwargs: ['is_preview']

[tjprescott]

@zikalino in regards to the is_preview kwarg, you need to have the latest bits from the dev branch. The min CLI core version for these commands is 2.0.66.