Extend AppBuilder api with `add_system_set` and similar methods#1453

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cart merged 3 commits intobevyengine:masterfrom TheRawMeatball:app-builder-add-system-set

Feb 19, 2021

+27-1

Commits on Feb 15, 2021

Extend API
TheRawMeatball
committed

Commits on Feb 19, 2021