updated RootConsole: moved to new _core package, modified structure to singleton
updated _core package (contains and exports basic console classes and BaseWidget class)
updated RootConsole singleton to decorator pattern
updated off_screen_console module and classes, extended decorator to render_wrapper
fixed module doc
updated BaseWidget with destroy method and documentation
fixed module doc
changed OffScreenConsole render phase logic to before/after methods, moved Screen classes
merge branch 'console_rework' into develop