Adding xmlisp as submodule

We are bringing xmlisp as a submodule and into the cl-3d system. This
reduced extenal dependency on XMLisp and saves the user an aditional
step of installing XMLisp.

However if this version of XMLisp makes it into quicklisp then we
could simply revert this commit.
Merge branch 'bring-xmlisp-as-submodule'
making a few changes in the shaders'
Need cl namespace for loop
Changing symbols to regular symbols for packages.

Eliminating the #: for all packages
Adding a new rendering (opengl) object to VR

Essentially VR class defines the environment. In general the environment
consists of input (devices) output (opengl for now) and scene which
reads data form input and renders itself to the output.

Note the OpenGL class is temporary for now. It should be replaced with a
general VR display API which can manage multiple graphics context. This
will be implemented in the future.