Unify the mdoc and Jupyter plotting support

[avibryant]

This PR:

• moves the plotting methods, as well as the println-based convenience methods, to the package object of a new rainier.notebook module
• changes all the plotting methods to return almond.display.Image instead of Drawable. This should be rendered directly in Jupyter (not yet tested).
• changes the evilplot mdoc modified that expected a Drawable to instead be image and expect a almond.display.Image

This lets us use the exact same methods in both contexts.

[codecov-io]

Codecov Report

Merging #463 into 0.3-dev will increase coverage by 0.23%. The diff coverage is 0%.

@@             Coverage Diff             @@
##           0.3-dev     #463      +/-   ##
===========================================
+ Coverage    53.04%   53.28%   +0.23%     
===========================================
  Files           72       71       -1     
  Lines         2771     2783      +12     
  Branches       172      166       -6     
===========================================
+ Hits          1470     1483      +13     
+ Misses        1301     1300       -1

Impacted Files	Coverage Δ
...in/scala/com/stripe/rainier/notebook/package.scala	0% <0%> (ø)
...la/com/stripe/rainier/notebook/ImageModifier.scala	0% <0%> (ø)
.../main/scala/com/stripe/rainier/core/SBCModel.scala	74.5% <0%> (-1.5%)	:arrow_down:
...src/main/scala/com/stripe/rainier/core/Trace.scala	8.33% <0%> (-0.56%)	:arrow_down:
...src/main/scala/com/stripe/rainier/core/Model.scala	57.4% <0%> (-0.29%)	:arrow_down:
...e/src/main/scala/com/stripe/rainier/core/SBC.scala	13.86% <0%> (-0.14%)	:arrow_down:
...rc/main/scala/com/stripe/rainier/ir/GraphViz.scala	0% <0%> (ø)	:arrow_up:
...rc/main/scala/com/stripe/rainier/compute/Vec.scala	0% <0%> (ø)	:arrow_up:
...ain/scala/com/stripe/rainier/compute/Decimal.scala	0% <0%> (ø)	:arrow_up:
.../com/stripe/rainier/ir/OutputMethodGenerator.scala	100% <0%> (ø)	:arrow_up:
... and 11 more

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