Initial release

support two modes:
gui mode, default mode a window will show. first, click open bimg file to open one. you can see the preview image. default type is RGB565 which is used in moflex video player as thumbnail. you can import/export bitmap, and save bimg file.
cli mode, used in converting scripts. bimg_conv filename.type the type can be bitmap or RGB565 bimg file. a new file with the same name will be created.
drug and drop support: just drag a bmp file or bimg file to the exe file, a new file will be created with the same name.
this requires .net framwork.