Also:
- Rename cache directory to .meteor
- Rename .meteor/version to .meteor/release
- Change how we tell whether we're in an app directory (motivated by our new .meteor directory)
- Use files.get_core_dir instead of relative paths
- No more global manifest. Instead, all functions requiring a manifest have it passed in, either
by argument or as a attribute on an appropriate object (such as BundleInstance)
- Some initial progress towards renaming project to app in the codebase
- Eliminate references to collections of packages as a type of "Package"
- Made meteor commands run correctly from a subdirectory of a meteor app, and
improved tests to have caught this.
- node.sh now returns the return value from the node executable
