Add WDL language support (#3858)

* Add WDL language support

* Add ace mode

samples/wdl/passingfiles.wdl

@@ -0,0 +1,42 @@
+# Sample originally from https://github.com/broadinstitute/centaur
+
+##
+# Check that we can:
+# - Create a file from a task and feed it into subsequent commands.
+# - Create a file output by interpolating a file name
+# - Use engine functions on an interpolated file name
+##
+
+task mkFile {
+  command { 
+    echo "small file contents" > out.txt
+  }
+  output { File out = "out.txt" }
+  runtime { docker: "ubuntu:latest" }
+}
+
+task consumeFile {
+  File in_file
+  String out_name
+
+  command {
+    cat ${in_file} > ${out_name}
+  }
+  runtime {
+    docker: "ubuntu:latest"
+  }
+  output {
+    File out_interpolation = "${out_name}"
+    String contents = read_string("${out_name}")
+    String contentsAlt = read_string(out_interpolation)
+  }
+}
+
+workflow filepassing {
+  call mkFile
+  call consumeFile {input: in_file=mkFile.out, out_name = "myFileName.abc.txt" }
+  output {
+      consumeFile.contents
+      consumeFile.contentsAlt
+  }
+}