Ability to display ConditionalNode

[cjllanwarne]

For example this nested if inside a scatter:

import "import_me.wdl" as import_me

workflow outer {
  Array[Int] xs
  scatter (x in xs) {
    Boolean b
    if (b) {
      call import_me.inner as inner { input: i = x }
    }
  }
  output {
    Array[String?] outer_out = inner.out
  }
}

Produces this rather delightful graph:

To save you some time:

• "Why is the Boolean b inside the scatter?"
  • Because https://github.com/broadinstitute/wdl4s/issues/217
• [X] "Why is the inner subworkflow not shown expanded too?" TODONE!

[mcovarr]

:+1: