add more params and functionalities taking advantage of GraphicsMagick

The added params are: - gravity: "-gravity" param, default is Center - crop: "-crop" param with "+repage" - rotate: "-rotate" param - monochrome: "-monochrome" param - grey: "-colorspace" param with "GRAY" - no_strip: "-strip" param - trim: "-trim" param - no_interlace: "-interlace" param with "Line". Useful for JPEG, I'm not sure about other formats. - flip: "-flip" param - flop: "-flop" param Please go to GraphicsMagick documentation for detailed explanation.

Added test functions for buildArguments.

Params parser now divided into 3 main parts to parse int, bool and string type params. Adding params is easier this way.

该提问来源于开源项目：pierrre/imageserver