Added plot library for megalogger, to diplay fancy dashboard

I prepared library for megalloger to display fancy dashboard. It provides 3 classes: CirclePlot, BarPlot and GPlot. It was needed to make public three methods of LCD_ILI9325D class in MultiLCD lib: setXY(uint16_t x0,uint16_t x1,uint16_t y0,uint16_t y1), WriteData(uint16_t c), WriteData(byte l, byte h). Now it is possible to use this library only with LCD_ILI9325D display, but changing insignificantly API for other types of displays would make possible to use this library with this too. It is needed also to update megalogger.cbp file.