Create a new `CopyTranscriptTask` as a subclass of `Task`

[cavis]

Second step of #969. Setup the async task to copy/process the transcript.

• [ ] Create a new CopyTranscriptTask as a subclass of Task
• [ ] To start, fire off porter Inspect / Copy tasks and parse the results back into the Transcript
• ~TODO: does Porter need any work to return the correct format/type for a transcript file? (cc: @farski)~
  • Update: punting on this till later. Detecting different "types" of transcripts is tricky.