Use omnijar as our chrome file format
    
    Don't bother passing a chrome file format in our mozconfig,
    omnijar is the default, but it didn't work before.
    
    Adjust the %files list accordingly.
    
    Move various bits to happen before running make install so they
    get automatically added to omni.jar.
    
    Make sure to add our prefs file to the manifest file so it gets
    pulled in, too.
    
    See http://blog.mozilla.com/mwu/2010/08/13/omnijar-how-does-it-work/