New .aunty output directory (replacing .build dir and .deploy file)

[colingourlay]

• Move built projects and deploy configurations into a .aunty directory, rather than creating two artefacts in the project directory.
• Rename build directory from .build to build so it's not hidden from file explorers by default
• Rename deploy configuration file from .deploy to deploy.json so that it gets syntax highlighting in editors.
• Update clean command to remove the .aunty directory
• Create an npm postinstall script which updates .gitignore files and clears old artefacts when aunty is upgraded in an existing project
• Update output artefact references in .gitignore file in project generator template