Work done:
* Improved button group layout of AF tool (See here)
* Core upgraded to v0.41
** Change the definition of scale (now it is number of pixel per unit).
** Both x and y axes use the same scale.
** Instead of specifying min and max for each axis, one needs to set up a range of value that an axis spans. The program will compute the respective min and max from translate_x and translate_y which tells the relative translation of the origin. -1 and 1 are the values for the two opposite edges.
** Fix aspect ratio of pCSDT tool. Changing the canvas dimension does not distort the grid. The grid drawing is now made to the whole visible area of the simulation canvas (see CC and GG), unless one sets bDrawGridBeyongRange to false (SB).
