graphics/twm4nx/src/window.cxx: Add flags to CWindow initializer to support customization of toolbar buttons and other window properties. Add framework to handle toolbar button presses. Window minimization (aka, iconification) does not work.
graphics/twm4nx/src/input.cxx: Add support to scaling touchscreen. Not needed for the current testing because the touchscreen naturally matches the display size. But will be needed, along with calibration scren, in the future.
Squashed commit of the following:
Clean-up some include path problems introduced with the previous set of changes.
app/include/graphics, apps/NxWidgets/UnitTests: Update include paths for file in new location.
apps/NxWidgets/nxwidgets and nxwm: Update include paths for file in new location.
apps/graphics/NxWidgets: Move nxwidgets and nxwm include/ directories to apps/include/graphics
