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.
It looks like the prefix comes from the setting EDX_ROOT_URL, which appears not to be set on edx.org... do you know what this setting is intended to be used for?