Added a placeholder in the OculusWorldDemo/Assets folder.  Noted extra requirement in readme.

As the assets folder is ignored it is not created when the repo is pulled from the server.  This masks the location until build time.

As the lack of the assets causes a build failure, this called for a note in the repository readme file.
Added ability to swap eye positions.

This allows the user to trivially swap the eye position by simply pressing the backslash "\" key.  The benefit of this is primarily targeted toward those of us who haven't enough pennies yet to purchase an Oculus unit: we can now do simple development of games that have at least output support for the HMD.