Preamble part of the primary main.tex

Some important changes
 - use "xcolor" package instead of "color" for the former provides more color facilities
 - rewrite the theorem environment for Q&A, only with the "amsthm" package (cause I'm not familiar with "ntheorem" package)
 - more new commands were added to the preamble, to help new TeX learners read (only the main.tex part) and use this template
 - move \FiveStar command from \textbf to \normalfont (default text style) situation, or the XeLaTeX will return a warning