功能绘图-简化版

Version 1.5: support for quick polynom typing (3x2+2x-2 - 3*x^2+2*x-2)Version 1.4: support for shorten typing (3x - 3*x)Version 1.3: support scientific notationVersion 1.2: support all sizes of screen (from 240x320 and higher), bug corrections.Version 1.1: GUI improvements, bug correction.Version 1.0: Initial version.