Specify package depth level of node_modules dirs to load tests from

Specify package depth level of node_modules dirs to load tests from
Use the same depth config to get yui modules config.

When doing a `mojito test`, mojito will run all the tests in the app (or npm bundle package) as well as all the tests it finds recursively in the node_modules.

In some occasions it is desirable to run only the first level of tests (without going into node_modules), or specify the depth level (0=app, 1, 2, etc).

This change add the capability in the yui rs addon to specify the depth, as well as the -d option in the `test` command to specify it in the command line.

The default behavior of including all tests is kept for backwards compatibility when the option is not specified.