Refactor buildApp for easier override
Refactor buildApp for easier override

This matches the changes to `Component`

RoundingWellOS/marionette.toolkit,paulfalgout/marionette.toolkit,TerrenceLJones/marionette.toolkit,TerrenceLJones/marionette.toolkit,paulfalgout/marionette.toolkit,paulfalgout/marionette.toolkit,RoundingWellOS/marionette.toolkit