allow for easier configuration of the loader

i'm opening this PR as a suggestion as to how loader config might be better handled.  

currently, when testing locally, only packages are supported in the query string and the whole JSON string needs to be provided.  i can see how that is useful when you're doing automated functional testing and the server can construct the appropriate query string but it's cumbersome and error prone to do manually.  this PR makes it possible to do client.html?suites=my/test/suite&loaderConfig=my/test/loaderConfig where my/test/loaderConfig is an AMD module that returns an object that is used to configure the loader.

this PR is only for client.js against the geezer branch because that's what i was working with at the time but if you like the suggestion, the full change would involve geezer and master branches as well as client.js and runner.js