Reorganized code: created Guard class

Reorganized code: created Guard class

Previously guards were not defined as a distinct class.

Since I want to build a conveniently manageable codebase which
would make a nice framework for my future additions, I need to
revise the actual post-LD code heavily.
The goal is to create a clean, well thought-out object-oriented
framework which is extensible and easy to depend on.
This is the first change towards that state, and seeing how
messy the code currently is, there will be many more.

	modified:   shapeshift.js