Add support for instructional comments per file

[jenschude]

At the moment when running the buildParameters script you get this advice:

Creating the "<file>" file
Some parameters are missing. Please provide them.

A nice to have to be able to configure the output per file. E.g.:

  "extra": {
    "incenteev-parameters": [
      {
        "file": "file.yml",
        "comment": "Login to your account and provide the API credentials here",
        ...
     }
    ]
  }
'''