Add support for java.util.Set for exported functions

[kipz]

From @snewman on November 23, 2016 6:11

Currently when returning collections from exported functions, only java.util.List is supported - it would be nice to add support for other collection types, specifically java.util.Set.

For the record, here is the stacktrace you get when using java.util.Set:

- should generate typescript file *** FAILED ***
  java.lang.UnsupportedOperationException: Unsupported type [Seq]
  at com.atomist.rug.ts.TypeScriptGenerationHelper.javaTypeToTypeScriptType(TypeScriptGenerationHelper.scala:35)
  at com.atomist.rug.rugdoc.TypeScriptGenerator$$anonfun$generateType$2.apply(TypeScriptGenerator.scala:82)
  at com.atomist.rug.rugdoc.TypeScriptGenerator$$anonfun$generateType$2.apply(TypeScriptGenerator.scala:73)
  at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:733)
  at scala.collection.mutable.ArraySeq.foreach(ArraySeq.scala:74)
  at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:732)
  at com.atomist.rug.rugdoc.TypeScriptGenerator.generateType(TypeScriptGenerator.scala:73)
  at com.atomist.rug.rugdoc.TypeScriptGenerator.com$atomist$rug$rugdoc$TypeScriptGenerator$$generate$1(TypeScriptGenerator.scala:119)
  at com.atomist.rug.rugdoc.TypeScriptGenerator$$anonfun$emitInterfaces$2$$anonfun$apply$3.apply(TypeScriptGenerator.scala:140)
  at com.atomist.rug.rugdoc.TypeScriptGenerator$$anonfun$emitInterfaces$2$$anonfun$apply$3.apply(TypeScriptGenerator.scala:140)
  …

[kipz]

Given that TS/JS/Rug don't support sets, I think it makes most sense to just use lists.