* clean : integrate I2C communication functions.
*I2C integrate (power.cpp + MPU9250.cpp) -> move to CommUtil.cpp (Cadd CommUtil class.)
*add debug flag for I2C communication (if use, defined I2C_DEBUG_TO_SERIAL in CommUtil.cpp)
*cleanup some comment and cords.(power.h)
Add :get a input key for M5Stack Faces
*add M5Faces.cpp and M5Faces class.
* Correction of rewriting mistakes
* Fix : refactoring code.
Modified to follow Arduino style guide as much as possible
*indent : 2spaces /tab
*format : UTF-8
*return : LF
* clean : integrate code format
* clean : integrate code format
*miss indent
* fix : replace to slash from '\' ( for multi-environment)
* fix:
*MPU9250.cpp : Correct the error of comment mark
*Sprite.cpp : Fixed the problem that the number of parentheses does not match due to the pre-processing condition
* fix : Refactoring mistake: number of parentheses did not match
*power function integrate to Power class.
*fixed M5.begin() : add I2C initialize flag.
*Check result after send I2C Request
*change method of send to power-ic register. (read->mask->write)