Rendering pipeline, Inputs, Debugger, and Bug fixes

This commit updates the rendering pipeline to use offscreen
page-flipping via two BufferedImage objects, thus fixing the original
"flicker" artifact.

Additionally, the initial work on establishing default key and mouse
inputs has been done.  This currently works in concert with the Scripts
bank, a collection of external Ruby source files encapsulated as Proc
objects which may be deployed as Runnable instances to the Thread Pool.
This behavior is experimental, as it results in multi-threaded
execution.

The debugging console is provided in this commit, and if the debug
environment variable or -d flag is present, it will be invoked.  It is
an attempt to emulate IRB-like behavior within the engine's runtime.

Bug fixes are also shipped, addressing scope problems, strange
behaviors, and potential concurrent access violations.