Indicate tests as a directory in package.json

- the blueprint for app/files/package.con indicated test not tests
Merge pull request #1934 from pixelhandler/package-blueprint-package-json

Indicate tests as a directory in package.json
Moved modulePrefix to config/environment.js
Merge pull request #1933 from jayphelps/module-prefix

Moved modulePrefix to config/environment.js
Allow addons to have public trees.

* Public is namespaced by default under the addons package name.
* Add simple easy to override method lookup pattern for customizing
  treeFor on a type by type basis.
Merge pull request #1930 from rwjblue/addon-public-tree

Allow addons to have public trees.
Ensure startApp helper users correct application params.
Merge pull request #1943 from rwjblue/ensure-start-app-uses-correct-params

Ensure startApp helper users correct application params.