Mp integration

Refs #95 

feat: Integrate with latest Marketplace back-end
    
    The API server root is now pointing at the server that provides marketplace data from the master branch. The Changes in
    this commit address several changes in that data:
    
    - Authentication is now required
    - Link rel names are qualified with prefix ozp:
    - Application listings are returned by specifying the appropriate HTTP Accept header
    
    The resource keys for applications are now generated as /applicatin/{uuid}. Previously the key was
    /application/{name}
    
    The enpoints and Ajax classes were modified to enable setting of request headers when loading data from the
    back-end server. The SystemApi data loading code now uses this to set the appropriate headers for retrieving
    the desired representation of application listing. Loading of the APIs has not yet been set to configure the
    appropriate Accept headers.