Use the Palaso library browser adapter

* Remove any direct gecko dependency from Chorus
* Remove the BetterBrowser in favor of using the XWebBrowser
  from the PalasoWindowsForms library
I think the #if false line of code here was in an abortive effort to avoid having to set LD_PRELOAD before running programs that use geckofx (even indirectly via chorus).  I would guess the effort wasn't successful, but the person who did it forgot to remove the experimental code.