/.boot/build.boot

Currently boot stores all of it's config files within the project root - I propose we also look in the project `.boot/` folder. This way we can keep projects from having an ever growing number of root project files, and keep boot files organized.

Not an important change but we would also align with more CD/CI tools which are doing the same. (ex `.circle/`)

Start by tracing how Boot discovers the project-root build.boot configuration named in the issue. Check which configuration files are considered, add support for the project .boot/ location, and verify that existing root-level configuration behavior remains unchanged.

Written by the indexing model from the issue text.