title: Combining 3 lists of tuples into one new list
body: <p>I'm new to scala and don't know what to do here.
  I have 3 Lists of tuples like:</p>
  
  <pre><code>List1 = List[(String,Option[String])]
  List2 = List[(String,Option[String])]
  List3 = List[(String,Option[String])]
  </code></pre>
  
  <p>The elements in the Lists could look like:</p>
  
  <pre><code>List1 = List[("a","1aa2"),("b","1bb2"),("c","1xx2")]
  List2 = List[("a","1aa2"),("b",None),("c","1yy2")]
  List3 = List[("a","1aa2"),("b","1bb2")]
  </code></pre>
  
  <p>The List could have different .size and the Optional field is sometimes empty.
  Now I want to combine these 3 List to a "resultlist" - which would look like this:</p>
  
  <pre><code>Listresult = List[(String,Option[String],Option[String],Option[String])]
  </code></pre>
  
  <p>which could look like</p>
  
  <pre><code>Listresult = List[
  ("a" , "1aa2"  ,"1aa2" , "1aa2"),
  ("b" , "1bb2"  ,  ""   , "1bb2"),
  ("c" , "1xx2"  ,"1yy2" ,   ""  )]
  </code></pre>
  
  <p>Is it possible to combine lists like that?</p>
  
  <p>thanks in advance</p>