Logger: Add possibility to send sync requests.

In this PR was done:
 - `*.coffee` -> `*.js`;
 - added possibility to set request parameters;
 - fixed and added new jasmine tests;
 - removed unnecessary `Courseware.prefix`.

@mulby, @andy-armstrong  please review.
In Studio we use the Backbone event dispatching mechanism, e.g.

https://github.com/edx/edx-platform/blob/master/cms/static/coffee/src/xblock/cms.runtime.v1.coffee#L19

See http://backbonejs.org/#Events for details.

In this case, it probably isn't worth the overhead, and maybe Backbone isn't loaded in all situations where we need this. Anyway, just a thought...