Use eslint --init to generate configuration

[Hirse]

The extension currently has a command to Create '.eslintrc.json' file, but I would prefer to use .eslintrc.yml.
This PR adds functionality to generate a Yaml file with the same settings as the JSON.

closes #409

[dbaeumer]

@Hirse thanks for providing this. However I am not a big fan of it to provide a VS Code command to create a YAML file. I would rather let the ESLint extension contribute a task to run eslint --init in the terminal which at the end will as you to pick the format you want to use. This is more flexible.

Would you be willing to look into this?

[Hirse]

@dbaeumer I agree that using eslint --init is cleaner.
Please see the last commit where I have replaced the config generation with running that command in the terminal.

[dbaeumer]

@Hirse thanks.

Some comments:

• to make this work in a multi folder setup the folder location must be passed as the cwd to the terminal. Otherwise the configuration might be created in the wrong location.
• what happens if eslint is only installed locally should the command then be .\node_modules\.bin\eslint instead.

[Hirse]

@dbaeumer Thanks for your comments and sorry for the delay.

I am passing the cwd to the terminal and reusing the existing logic to find the location of the ESLint location. I have extracted that functionality to a new file as it doesn't entirely belong to the tasks.

[Hirse]

Thanks for merging, but I just saw that the Readme needs to be updated:
https://github.com/Microsoft/vscode-eslint/blob/4303aa4075905ffc2c37dc4bee7e36d4526953ad/README.md#L7

I might be able to open a PR later today if you didn't get to it by then.

[dbaeumer]

Done.