code cleanup: Make frames get constructed cleanly

[sittr7]

See nav -> FrameFactory

• possible solution: have model construct all frames as objects initially.

  • caveat: makes Model depend on View

• possible solution: give each dumb data frame a property saying what type of frame it is

  • FrameFactory uses this property to decide what Frame type to construct, rather than other arbitrary properties of the dumb data frame
  • they already have this property ("template") in sample_app.
  • just need to add the "template" property and set it to the correct value within dbt_worksheet_model.
  • build_intro_frames
  • build_body_frames
  • initialize_summary_frame

[sittr7]

Done on the spot 😼 😸