have sbt use more heap by default

because why not? RAM is cheap these days. and today I kept getting
OutOfMemoryError when starting up sbt. and we've seen occasional
OutOfMemoryError on Travis
Tortoise: remove __ask-sorted

we're not using it anymore, and as we work up to the Tortoise repo
split we're looking to minimize differences between the tortoise
and headless branches outside of tortoise-specific directories
Tortoise: get DummyShape out of api package

it's only used in tortoise.dock, and as we work up to the Tortoise
repo split we're looking to minimize differences between the tortoise
and headless branches outside of tortoise-specific directories
Merge remote-tracking branch 'origin/headless' into tortoise