Introduced a BaseGauge class which TfpgGauge descends from.
Introduced a BaseGauge class which TfpgGauge descends from.

- Also made the various xxxDraw methods virtual and moved them to the
protected section. So they can be overridden in descendants if needed.

- Fixed the default color value of the Color property. The value stored
in RTTI was different to the actual value assigned in the constructor.

wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI