title: How to add multiple outlets for generated XText DSL
body: <p>By default the generated XText artifacts generate code from my DSL to the default outlet (which defaults to src-gen folder). I know that you can explicitly pass the outlet configuration name in fsa.generateFile("myfile.txt", "MY_OUTLET_NAME", "Some file content").</p>
  
  <p>I it because I want to generate code with my XText DSL and want to use the generation gap pattern and generate code in a folder called "src-once".</p>
  
  <p>I'am using XText 2.2.1.</p>
  
  <p>My questions:</p>
  
  <p>1) Where and how do I define my outlets like "MY_OUTLET_NAME"?</p>
  
  <p>2) Is there a way to prevent overwriting existing files in a specific outlet?</p>