Added ButtonLogic Class

Added ButtonLogic Class
    src/model/ButtonLogic.cpp   (+)
    src/model/ButtonLogic.h     (+)
    src/model/TestButtonLogic.h (+)
Added Timer class

Added Timer class
Based on SDL timer. Consider replacing with C++11 chrono.
    util/TestTimer.h (+)
    util/Timer.cpp   (+)
    util/Timer.h     (+)
Cosmetic: header ordering rules

Cosmetic: header ordering rules
    model/TestButtonLogic.h
    script/TestScriptEngine.h
    util/TestException.h
    util/TestFileUtil.h