Add WDL language support (#3858)

* Add WDL language support

* Add ace mode

samples/wdl/hello.wdl

@@ -0,0 +1,21 @@
+# Sample originally from https://github.com/broadinstitute/centaur
+
+task hello {
+  String addressee
+  command {
+    echo "Hello ${addressee}!"
+  }
+  output {
+    String salutation = read_string(stdout())
+  }
+  runtime {
+    docker: "ubuntu@sha256:71cd81252a3563a03ad8daee81047b62ab5d892ebbfbf71cf53415f29c130950"
+  }
+}
+
+workflow wf_hello {
+  call hello
+  output {
+     hello.salutation
+  }
+}

samples/wdl/ifs_in_scatters.wdl

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+# Sample originally from https://github.com/broadinstitute/centaur
+
+task validate_int {
+  Int i
+  command {
+    echo $(( ${i} % 2 ))
+  }
+  output {
+    Boolean validation = read_int(stdout()) == 1
+  }
+  runtime {
+    docker: "ubuntu:latest"
+  }
+}
+
+task mirror {
+  Int i
+  command {
+    echo ${i}
+  }
+  output {
+    Int out = read_int(stdout())
+  }
+  runtime {
+    docker: "ubuntu:latest"
+  }
+}
+
+workflow ifs_in_scatters {
+  Array[Int] numbers = range(5)
+
+  scatter (n in numbers) {
+
+    call validate_int { input: i = n }
+    if (validate_int.validation) {
+      Int incremented = n + 1
+      call mirror { input: i = incremented }
+    }
+  }
+
+  output {
+    Array[Int?] mirrors = mirror.out
+  }
+}

samples/wdl/passingfiles.wdl

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+# 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
+  }
+}