Making some asynchronous operations synchronous when creating a noder context.

This commit replaces some calls to "then" by calls to "thenSync" to make
some operations done during the creation of a noder context synchronous
if possible.
Using synchronous promises and requests to display error messages.

This simplifies the code and provides a better report of the errors
to the developer.
Fixing a double error message when failing to load a module.
Using atpackager for the build.
Adding an atpackager visitor to generate a file containing a set of calls to require.